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The Whole Story with Anderson Cooper

The Gilgo Beach Killer. Aired 8-9p ET

Aired July 23, 2023 - 20:00   ET

THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.


[20:00:29]

ANDERSON COOPER, CNN HOST: Welcome to THE WHOLE STORY. I'm Anderson Cooper.

In December of 2010 four bodies were found along a quarter-mile stretch of Gilgo Beach on the South Shore of Long Island, New York. All four victims were young women in their 20s who'd advertised sex work on Craigslist. Their bodies were found within a quarter-mile stretch of beach. They were all bound at the feet or ankles and covered with burlap to hide them.

It was a shocking discovery, and it was just the beginning. Over the next year seven more sets of human remains were found in the area, most of them women.

So was this the work of a serial killer? That's the question investigators have been asking for more than a decade with no answers until 2022, when recent DNA technology gave police a new lead. They now have a suspect, someone they say was living a double life as a husband and a father. Police feared he was targeting even more victims.

Over the next hour CNN's Brynn Gingras will piece together how exactly police were able to I.D. the suspect and how the possible killer was able to get away with it for so long.

(BEGIN VIDEOTAPE)

UNIDENTIFIED FEMALE: State police.

SHANNAN GILBERT, VICTIM: There's somebody after me.

UNIDENTIFIED FEMALE: What's your name?

GILBERT: Shannan Gilbert.

UNIDENTIFIED FEMALE: Where are you?

GILBERT: I'm in Long Island.

UNIDENTIFIED FEMALE: And what's wrong?

GILBERT: These people are trying to kill me.

BRYNN GINGRAS, CNN NATIONAL CORRESPONDENT (voice-over): May 1st of 2010.

GUSTAV COLETTI, OAK BEACH RESIDENT: She showed up at my door and she's banging on the door screaming, help me, help me, help me.

GINGRAS: Shannan Gilbert, a 23-year-old woman working as an escort, has been brought to a house party near Gilgo Beach. On a picturesque barrier island an hour east of New York City. Something or someone prompted Gilbert to call police, run from the party, and then toward the beach.

COLETTI: That was the last I saw of her.

GINGRAS: Shannan Gilbert had disappeared. Months later.

OFFICER JOHN MALLIA, SUFFOLK COUNTY POLICE DEPARTMENT: Missing persons unit called us out on Saturday to follow up on an investigation on a missing person.

GINGRAS: During a search for Gilbert an officer and his cadaver dog make a startling discovery.

MALLIA: At some point the dog gave me an indication, which means its tail started waving. He started sampling the air. At that point I saw the skeletal remains of a body.

RICHARD DORMER, FORMER SUFFOLK COUNTY POLICE COMMISSIONER: There's no indication that this is Shannan from May 1st of this year.

GINGRAS: It wasn't Shannan Gilbert. And it wasn't just one body.

MALLIA: We were quite surprised the second day when we found the second body. It was approximately 500 feet west of the first body and then we conducted a more detailed search and we found a third body and then ultimately the fourth body. All within about 500 feet of each other.

GINGRAS (on-camera): Can you give more details about how they were found?

ERROL TOULON JR., SUFFOLK COUNTY SHERIFF: Most of the victims were all bound. Feet and hands.

RAYMOND TIERNEY, SUFFOLK COUNTY DISTRICT ATTORNEY: Their bodies were covered in a camouflage burlap, type of burlap that's used to obscure duck hunting blinds or cover a boat when you're hunting for ducks.

DORMER: It looks like a car pulled up and opened the door and the bodies were dumped.

JOHN MILLER, CNN CHIEF LAW ENFORCEMENT AND INTELLIGENCE ANALYST: Some of these bodies have been there more than a year or so. There's clothing missing, and there's personal effects missing. So that is telling us we have someone who is taking their lives and keeping parts of them, an article of clothing, a personal effect. The term that they use in the serial killer genre is trophies from his killings. GINGRAS (voice-over): Long Island has a serial killer. A little more

than a month later the public would learn the identities of the victims.

DORMER: The victims are Maureen Brainard-Barnes of Norwich, Connecticut. Amber Lynn Costello of North Babylon, New York. Megan Waterman of Scarborough, Maine. And Melissa Barthelemy of the Bronx.

[20:05:05]

JEFF MARTIN, MELISSA'S STEPFATHER: We actually were watching the news and we saw that there were four bodies found on Long Island. They actually showed the remains of one of the skeleton.

LYNN BARTHELEMY, MELISSA'S MOTHER: They showed the remains.

MARTIN: And we just started bawling. There's something that pulled us.

BARTHELEMY: And we just -- we know it was her.

UNIDENTIFIED MALE: What seemed familiar about it?

BARTHELEMY: Just the size of the remains.

GINGRAS: Melissa Barthelemy was petite and in her 20s, like all the other victims.

MILLER: He was very selective about people under five feet. He wanted young women who appeared younger by their size.

GINGRAS: It wasn't the only similarity.

DORMER: All of them were self-employed in the escort business. They were soliciting their services on Craigslist and other Web sites found on the internet.

MARTIN: No matter what she did she was my daughter and a good friend to people.

MARK SZPILA, MELISSA BARTHELEMY'S FATHER: I would just like to put it out there that she was the light of my life. I'd just like to set the record straight that she wasn't a mean person and she wasn't a bad person.

ROBERT KOLKER, JOURNALIST AND AUTHOR, "LOST GIRLS: AN UNSOLVED AMERICAN MYSTERY": I bought into all the horrible stereotypes about victims in crimes like this. I assumed they lived off the grid and that no one was looking for them. In fact, their families have been looking for their lost loved ones, some of them for months, and one for 3 1/2 years, one for two years.

GINGRAS: That was the Barthelemy family whose daughter Melissa's initial disappearance in 2009 was followed by multiple phone calls to her 15-year-old sister Amanda by someone who claimed to be her killer.

MILLER: The calls come in from Melissa's phone. This is quite jarring because she's been missing and you see her caller I.D. come up and her 15-year-old sister answers.

BARTHELEMY: He was taunting her. He was basically torturing her. She kept asking where her sister was, and he just wouldn't tell her. She would ask, you know, if she was alive. He wouldn't answer. I mean, we always had hope until that last call when he told Amanda that he killed her.

MILLER: It was singularly the most chilling, disturbing but also cruel thing you could do to a victim's family, especially a sister, a teenage girl who was searching for answers and trying to cling for hope.

GINGRAS: Hope that was fueled when police began tracing those calls. But that led nowhere.

STEVE COHEN, ATTORNEY FOR MELISSA BARTHELEMY'S FAMILY: The caller made sure that he called from very busy areas. Madison Square Garden, Times Square. So that the cameras and the web cams that are out there would look down into a crowded field and at any given time there were at least dozens of people who were talking on a cell phone.

GINGRAS: At the time the Gilbert family was holding out hope, too.

KOLKER: After those first four women were found the police announced that they were going to keep looking for Shannan Gilbert. And in the months after those women were discovered they did find more human remains.

NANCY GRACE, TV HOST: In the last hours, another body believed to be that of a fifth woman turns up on that same stretch.

KOLKER: And then they found more.

UNIDENTIFIED REPORTER: Eight bodies discovered on Gilgo Beach. This is out on Long Island. Three were found just yesterday.

KOLKER: And then they found more and then they found more. And in all something like 11 people were found who may or may not be connected to one another, may or may not been connected to those first four women.

GINGRAS: All of them in the area around Gilgo Beach and none of them Shannan Gilbert. And as the bodies piled up, so did the concerns.

(On-camera): Can you talk about Gilgo Beach, the tension that I imagine was arising after these discoveries?

TOULON: When you start to have several murder victims and those bodies have been there for quite some time, it brought tremendous, tremendous fear within that community.

GINGRAS (voice-over): Which was usually a tranquil place.

TOULON: These are communities of individuals that love to be around a beach. They like to enjoy the better part of life with peace and quiet. And if you think along that long strip of highway along Gilgo Beach, it's a peaceful drive, it's a peaceful walk. [20:10:00]

GINGRAS: And it's something else, too. An ideal spot for the end of a violent spree.

MILLER: It's a near perfect burial ground. Not far off the road. You're in a wooded area. A few feet more you're in marshes with water, tall grass. And when you get to the road, you can look miles in one direction or the other, and see anything coming in terms of a car or a person. It gives you a real chance to work unobstructed, particularly at night in the dark.

GINGRAS: By the end of 2011 police would finally find Shannan Gilbert's body, three miles from the so-called Gilgo Four. And then another surprise in a case full of them. Police let it be known that they didn't believe Gilbert's death was connected to the hunt for a serial killer, the one that her disappearance helped launch.

It's an investigation that lay dormant for a decade, until a new way of looking at the case changed everything.

RODNEY HARRISON, SUFFOLK COUNTY POLICE COMMISSIONER: Today's a good day.

(COMMERCIAL BREAK)

DORMER: Well, our theory is now that there's one killer involved. We're leaning towards the one serial killer scenario.

GINGRAS: One year after the remains of four missing women were found here bound in burlap and dumped in the marshland of Long Island's Great South Bay, the quiet town of Gilgo Beach had plunged into a fog of fear. And the investigation into the murders showed little sign of progress.

UNIDENTIFIED MALE: I think that the facts that have been disclosed so far do not bear out a single killer theory at all.

KOLKER: An investigation like this, you'd think every single agency would want to collaborate to try to get the killer. But here in Suffolk County you had a police force that was kind of at odds with the district attorney. The collaboration was really, really compromised from the very beginning.

MILLER: You had a very dedicated team of investigators, but you also had a police department that was going through the throes of dysfunction, corruption and investigations into itself.

UNIDENTIFIED REPORTER: Do you have anything else to say?

[20:15:06]

MILLER: You have the chief of the county police department under investigation by the FBI, who was also investigating the district attorney. KOLKER: It meant that outside agencies like the FBI, who might be

inclined to investigate this corrupt official, were being kept away from the case.

GINGRAS: Another problem, some say, was that investigators lacked the motivation to solve these murders from the start.

KOLKER: From the very beginning it was abundantly clear that if these murder victims had been college students or corporate workers that the case would have been taken much, much more seriously. It was very clear that there was victim blaming going on. It couldn't help but impact the case.

DORMER: I don't want anybody to think that we have a Jack the Ripper running around Suffolk County with blood dripping from a knife.

UNIDENTIFIED FEMALE: I think that it was very comforting when we found out that he was targeting a specific group of women so that it made it something that was removed from us.

GINGRAS: Between the scandal-ridden police department, nearly a dozen sets of remains and a marginalized group of victims, the Gilgo murder case officially went cold, frozen it seemed for years, until a gradual shift in leadership opened the door to a fresh start.

KOLKER: One of the great things about Geraldine Hart becoming commissioner in Suffolk County is that she had spent her career at the FBI. And so this is an amazing moment where not only was she able to get people from the FBI and people from the Suffolk County Police Department to work together on a regular basis on this case, she also was able to talk to folks in the FBI about DNA analysis, all sorts of scientific techniques that a police department like Suffolk just wasn't able to do.

GERALDINE HART, FORMER SUFFOLK COUNTY POLICE COMMISSIONER: Good afternoon and thank you for joining us.

GINGRAS: To many's surprise, in 2020 Commissioner Hart held an unexpected press conference on the case, revealing a new clue for the first time in years.

HART: A black leather belt embossed with the letters HM or WH was recovered during the initial stages of this investigation. We believe that the belt was handled by the suspect and did not belong to any of the victims.

KOLKER: A short time after that press conference Geraldine Hart had another press conference announcing that they had successfully identified another victim.

HART: Today we are announcing that Jane Doe number six has been positively identified as Valerie Mack.

KOLKER: And that to me was a suggestion that this police department was starting to get serious and that they were really rolling up their sleeves and getting to work. GINGRAS: The work continued into the next administration. In 2022 NYPD

veteran Rodney Harrison replaced Hart as the new Suffolk County police commissioner, and one of his first moves was to launch an interagency task force dedicated to solving the Gilgo murders.

(On-camera): When you took office, why was it so important for you to start this task force?

HARRISON: I wanted to make sure that we're working with all of our law enforcement partners. The objective was to put a dragnet out there, see what we could do to see if we could get as many people to participate, reach out to their networks, and see if we could get closer to identifying a subject. Then it paid off.

GINGRAS (voice-over): One of the first important leads that caught the attention of the new task force came from a witness who told investigators that the night before victim Amber Costello's disappearance a client arrived at her home and they described him.

MILLER: 6'4", 250 pounds, a big mop of hair. Giant 1970s type glasses. The witness said he was huge, he looked like an ogre.

GINGRAS: Investigators also obtained Costello's cell phone records, which revealed that a burner phone number contacted her that night, just before the client entered her home. The following night, on September 2nd, the same burner cell phone contacted Costello again. Shortly after, Costello left her house and a witness spotted a dark green-colored vehicle nearby.

MILLER: So the state police investigator started to work on the car, and she says I'm going to enter the search as a green pickup truck. And it comes back to Chevy Avalanche. It's in South Carolina registered to a guy. But it used to be registered right here.

Who was it registered to? Rex Heuermann. OK. Who's Rex? They run him. No criminal record. Well, what does Rex look like? He's 6'4". He's 250 pounds. He wears big round glasses. He's got a mop of hair. He's got a green truck.

[20:20:02]

HARRISON: I'm not sure when I exactly said that's our guy, but I will say this. When we were able to track back that green Avalanche is when I was like, OK, we're getting close.

GINGRAS (on-camera): The car.

HARRISON: The car. Exactly.

GINGRAS (voice-over): Investigators kept digging. And they discovered that just like Costello cell phone records from victims Melissa Barthelemy and Megan Waterman were contacted by burner phones in the hours before they disappeared. But it was the locations where those burner phones pinged that was most interesting.

LAWRENCE KOBILINSKY, FORENSIC SCIENTIST: What they were able to do is narrow down the area where the phones were pinging to an area in Midtown Manhattan around 5th Avenue and 35th Street, thereabouts, and another area in Massapequa, Massapequa Park on Long Island.

GINGRAS: Both are locations key to Rex Heuermann. His office in Midtown Manhattan and his home in Massapequa Park. Just across the bay from the Ocean Parkway where the bodies of the Gilgo Four were discovered.

NATHAN LENTS, BIOLOGY PROFESSOR, JOHN JAY COLLEGE OF CRIMINAL JUSTICE: I think the big breakthrough with the task force was the use of the cell phone records.

GINGRAS: Nathan Lents is a professor at John Jay College of Criminal Justice in New York City.

LENTS: That allowed them to identify the location in Manhattan and the location on Long Island, and they were able to connect it to his cell phone pings as well. So he was using a burner phone, but in his pocket was his regular cell phone, which was also making pings. So they were able to connect those two. So even the use of a burner phone did not conceal his identity like he hoped it would.

GINGRAS: Further investigating confirmed that over the years Heuermann frequently used burner phones to contact sex workers and as recently as May 2023 investigators spotted him purchasing additional minutes linked to a burner cell phone.

MILLER: He is growing into the suspect because you now have a car. You have a face. You have the geographic connection. But that is circumstantial. They need that thin hair of evidence that is going to go from circumstantial to certainty. And the thin hair of evidence turns out to be a thin hair.

KOLKER: Two of those hairs apparently, according to the document that we've read, can be connected to his wife and one of them can be connected straight to him.

MILLER: Now we're in a different place.

HARRISON: Today's a good day.

GINGRAS (on-camera): What did it feel like to tell the public we got the guy, this is who he is?

HARRISON: It felt good. It's the reason why I became a police officer.

Ladies and gentlemen, Rex Heuermann is a demon that walks among us.

I know it's been a long time coming. There might have been some things that we could have been better, but we're here today and we're announcing that we're placing this animal under arrest.

GINGRAS (voice-over): Up next, who is Rex Heuermann?

REX HEUERMANN, SUSPECT: I think it's taught me more about how to understand people. (COMMERCIAL BREAK)

UNIDENTIFIED MALE: Serial killers are skillful at presentation of self. They're extraordinarily ordinary.

HEUERMANN: I'm an architect. I'm an architectural consultant. I'm a troubleshooter. Born and raised on Long Island.

GINGRAS: This is Rex Heuermann in February of 2022.

HEUERMANN: Selfie time.

UNIDENTIFIED MALE: Selfie time. One, two, three.

GINGRAS: The YouTube channel Bonjour Realty was interested in Heuermann's Manhattan-based architecture and consulting firm.

UNIDENTIFIED MALE: What has this job taught you about yourself?

HEUERMANN: I think it's taught me more about how to understand people.

GINGRAS: Now an accused serial killer, police are struggling to understand him.

(On-camera): What was his personal life like?

TOULON: We're still learning more and more about who he is. No one that he worked with or no one that hired him or his firm ever brought anything to our attention.

GINGRAS: This isn't a guy who you have police going to his house often for calls for service.

TOULON: Correct.

GINGRAS: Even surveilling him. He seemed normal, going about normal patterns.

TOULON: It was like everyday life. He never did anything. He was just a normal, peaceful law-abiding citizen.

GINGRAS: What surprised you the most about Heuermann?

KOLKER: I was surprised that he had a family. I was surprised that he had such a high-profile job. I really expected somebody who kept to himself, who wasn't hiding in plain sight.

GINGRAS (voice-over): For decades Heuermann, his wife and two children lived here, in Massapequa Park on Long Island, New York.

STEVE, MASSAPEQUA PARK RESIDENT OF 20 YEARS: It's a great neighborhood. Good schools. Nice area. Houses are mostly well-kept.

GINGRAS: Among the properties in the Shoreline Village Heuermann's home stands out.

STEVE: Anybody who drives by always is looking. It's kind of an eyesore.

JOSEPH, MASSAPEQUA PARK RESIDENT OF 18 YEARS: It's on my block and Halloween came, I just said don't trick or treat there.

[20:30:02]

JOHN, MASSAPEQUA PARK RESIDENT OF SIX YEARS: That house just doesn't look right. But you never thought that there was actually anything happening.

GINGRAS: A source involved in the investigation believes Heuermann may have lured the victims to his home, killed them there, and then dumped the bodies.

TOULON: Every time a murder was committed his wife was out of the state.

GINGRAS: Heuermann's wife was in Maryland when Megan Waterman went missing, according to authorities. New Jersey when Amber Lynn Costello vanished. And Iceland when Melissa Barthelemy was last seen.

(On-camera): You probably have learned that his wife of 20 years has filed for divorce.

HARRISON: I heard that.

GINGRAS: You don't think she knew?

HARRISON: I don't think she knew. She was heartbroken. Also, speaking to the daughter, speaking to the son, giving them the information, the horrible news, I'm being told that they were embarrassed.

JAMES ALAN FOX, PROFESSOR OF CRIMINOLOGY, LAW AND PUBLIC POLICY, NORTHEASTERN UNIVERSITY: It's quite common for serial killers to have good jobs and families, wives and kids, whom they care about and who have no idea what they're doing in their free time when they have literally some free time to kill.

John Wayne Gacy, who while his wife was away he would have young men over, and he'd bury the remains of 29 of his 33 victims in the crawlspace of the house. And his wife would ask him, what's that odor? He said it's the sewer gases and I'll take care of it.

GINGRAS: Heuermann's home, office and storage units were scoured for evidence.

(On-camera): Office furniture, a "Playboy" magazine, an arsenal according to authorities of guns was found in the basement of that home.

MILLER: He's got 92 guns registered to him at home. And they find out that it's not 92 guns, it's somewhere between 200 and 300 guns. These are pistols, revolvers, semi-automatics.

GINGRAS: What sort of items are you looking for?

HARRISON: Jewelry. Anything that could be attached to the women.

MARY ELLEN O'TOOLE, FORMER FBI PROFILER: The serial sexual killers will very likely take what we call a souvenir from a victim.

GINGRAS (voice-over): FBI profiler Mary Ellen O'Toole has investigated serial murder cases for nearly three decades.

O'TOOLE: That souvenir could be a lock of hair. It could be a body part. It's important to them because it enables them to relive and re- fantasize about what they did.

FOX: Joel Rifkin, another Long Island serial killer, kept souvenirs, his victims' jewelry, clothing, kept them in his bedroom.

GINGRAS: The hunt to find more evidence and possibly more alleged victims has expanded across the country.

KOLKER: He did travel. He did have a residence somewhere else.

GINGRAS (on-camera): Do you believe there are more victims out there?

KOLKER: I think someone this organized, someone who is this determined, that person doesn't quit.

GINGRAS (voice-over): Authorities are now actively investigating Heuermann's connections to Nevada, South Carolina, and New Jersey.

(On-camera): Heuermann and his wife owned condos in Las Vegas. Can you give any insight into the investigation happening in Nevada?

HARRISON: I just know we're working with the local officials out there trying to track down anything that they may have out there.

GINGRAS (voice-over): Tax records show Heuermann also owns four large plots of land in northern South Carolina.

(On-camera): What did you find in South Carolina?

HARRISON: The only thing we found is the truck. That's the only reason why we went down there, is to bring the truck back and make sure it's processed. We're going to look through it and see what we can potentially recover.

GINGRAS (voice-over): The truck was a green Chevrolet Avalanche. When one of the women Heuermann is accused of killing disappeared, a witness told investigators they saw the killer driving a green pickup according to two law enforcement sources with knowledge of the case. Authorities also believe Heuermann may have ties to other unsolved murders in Atlantic City.

TIERNEY: We were able to get his Google searches off of a particular fictitious e-mail address.

GINGRAS: Online, Heuermann's Google search history reveals a troubled mind fascinated by his alleged murders.

TIERNEY: He was sort of obsessively searching for details about the Gilgo Beach investigation.

O'TOOLE: It's extremely common for these offenders to follow their cases in the media.

FOX: Dennis Raider, he came up with his own moniker, BTK for bind, torture, kill, hoping that that moniker would make him a little bit more newsworthy.

DOMINIQUE VIDAL, WITNESS: He asked me do I know about the Gilgo Beach murders.

GINGRAS: Dominique Vidal met Heuermann through a networking group for business owners.

VIDAL: He goes on to tell me, yes, that's a serial killer that was never caught in my hometown, my neighborhood where I live, and tells me he like -- the guy killed 10 people and he might still be out there.

[20:35:11]

I just cannot stop running that conversation over and over in my head, and I'm really disturbed.

GINGRAS: In February, Heuermann left Vidal this voicemail.

HEUERMANN: I actually heard you are no longer part of the group. I still wanted to talk to you. I had a question for you. And also wanted to touch base. Hope you're doing good. Hope to talk to you soon.

VIDAL: I found it odd he was calling me because he had no work for me. I had no work for him. There was no ongoing relationship. We were just two people who used to be in the same networking group.

GINGRAS: Heuermann, seen here being transferred to the Suffolk County Correctional Facility, has pleaded not guilty. Charged with the murders of Melissa Barthelemy, Megan Waterman, and Amber Costello.

UNIDENTIFIED MALE: The only thing I can tell you that he did say as he was in tears was, "I didn't do this."

GINGRAS: The accused killer is scheduled to appear in court on August 1st.

UNIDENTIFIED MALE: We're looking forward to fighting this case in a court of law, not in the court of press.

GINGRAS: When we return --

TOULON: One of the smoking guns is he has some pizza.

GINGRAS: The groundbreaking DNA technology that cracked the case.

LENTS: This was I think one of the first cases that were pursued using this technology.

(COMMERCIAL BREAK)

[20:41:51]

JOHN BERMAN, CNN ANCHOR: A string of murders that terrorized Long Island for more than a decade possibly solved today.

WOLF BLITZER, CNN ANCHOR: Disturbing new details about a suspected serial killer.

JAKE TAPPER, CNN ANCHOR: The first arrest in their decade-long investigation into the Gilgo Beach murders.

GINGRAS: July 14th, 2023. Investigators reveal key evidence that helped them crack the case. Hairs found on the victims' bodies more than a decade ago.

TIERNEY: The crime scene, because it was exposed to the elements, those hairs were degraded so you couldn't use traditional DNA analysis on it.

So the five hairs, there was one hair that was found on Maureen Brainard-Barnes. Her legs were bound by a belt. There was a hair that was adhered to the belt. Megan Waterman, there were three hairs found on her. Amber Costello, there was a hair that was recovered from the burlap.

KOBILINSKY: Ten years ago the police actually used the nuclear DNA analysis. They attempted to do it. But it failed because they couldn't get enough information.

GINGRAS (on-camera): Would you say the new DNA testing was a break in the case?

TOULON: Clearly the new testing was the biggest break in our case. We would not have been able to do this in 2010 because this technology wasn't available.

GINGRAS (voice-over): While the 2022 task force investigation that ultimately led to Rex Heuermann's arrest was undeniably exhaustive and detailed.

LENTS: This kind of manhunt is pretty unprecedented.

GINGRAS: Sixteen months of surveillance, cell phone signals triangulated, security footage scanned, internet searches, e-mail accounts accessed, credit cards and travel records scoured. But experts agree that one tool tipped the scales.

LENTS: It was DNA that eventually led to a definitive identification. DNA technology is probably advancing faster than almost any other biotechnology you can think of. Even faster than computing.

GINGRAS: DNA expert Nathan Lents points out that evidence gathered now may take years to yield results as science advances.

LENTZ: And the remains were put in a burlap sack rather than plastic. So they were more subjected to the elements. The evidence begins to get erased, like an Etch-a-Sketch over time with weather. Evidence does eventually wash away, disappear, blows away and just decays.

KOLKER: One of the big questions on this case for the last 12 years was, was there DNA at all? The police weren't saying. It turns out there was but it was so minuscule that it took a new leveling up of the technology to mitochondrial DNA for them to do the kind of analysis that was able to connect them to this suspect.

GINGRAS: In 2020 the FBI launched that next-level DNA testing with new protocols for forensic crime labs.

LENTS: So this was one of the first cases that were pursued using this technology.

KOBILINSKY: The shaft of the hair has mitochondrial DNA. Over time and decomposition the root disappears and all you have left is the shaft.

[20:45:04]

LENTS: Mitochondrial DNA is much smaller and it's much more robust. So it lasts a much longer time. It's present in hair samples. Even if you don't get a root.

KOBILINSKY: All you need is about one centimeter length of that hair to get a genetic profile.

GINGRAS: And those microscopic bits of hair would eventually lead to a breakthrough.

LENTS: There were hairs identified on one of the remains that were not from the victim. The problem is they didn't have anyone to compare it to.

GINGRAS: Enter Suffolk County police detectives working undercover to surveil Heuermann.

LENTS: So they began collecting evidence from his home.

KOBILINSKY: The surveillance team picked up 11 bottles and brought that to the lab. They swabbed the bottles, collect the DNA.

LENTS: But it did not belong to the alleged perpetrator. It belonged to his wife.

TOULON: She was not even in the state when any of these murders occurred.

KOBILINSKY: And so it becomes a case of hair analysis.

LENTS: It's not unusual that he would have transferred hair from his wife to his victims.

KOBILINSKY: Hair is ubiquitous. People lose scalp hair about 125 a day just from life, from living. And that hair tends to stick to clothing.

LENTS: You can have DNA from someone that you've been in contact with for days later.

KOBILINSKY: In this case they found three female hairs on two of the bodies and they found a male hair on one of the victims.

GINGRAS: The key question, did that male hair belong to their prime suspect?

MILLER: So what they need from Rex Heuermann is DNA. A surveillance team is sent to Midtown Manhattan, the area where he works, and they're basically watching the building. And he comes out and he goes to a pizza place, and they see him go through three slices of pizza. And he takes the box and shoves it into the green trash can.

DAVID SARNI, RETIRED NYPD DETECTIVE: So that was a treasure trove of DNA in there with that pizza box.

MILLER: So from a chain of custody standpoint they've seen him eating it, and carrying it, they've seen him discard it, and they pull that box out.

UNIDENTIFIED MALE: We're able to test it with his DNA to match the DNA at the crime scenes.

TIERNEY: One hair matched the DNA profile, that of the defendant Rex Heuermann.

GINGRAS: Just one month after these lab results police have enough evidence to make the arrest. Local TV cameras captured him in custody.

UNIDENTIFIED REPORTER: Rex, did you do it?

UNIDENTIFIED REPORTER: Fifty-nine-year-old Rex Heuermann is believed to be responsible for murdering multiple women.

UNIDENTIFIED REPORTER: We saw investigators putting on those full body Tyvek suits going into the home of Rex Heuermann.

TAPPER: Suspected serial killer has been arraigned.

MILLER: This is the kind of case a prosecutor wants.

SARNI: The cell phone records, the computer searches, the DNA recovered from the scene. Very strong evidence to prosecute this case.

MILLER: So it's a real triumph of law enforcement. What you're looking at is a new genre of investigation because it combines classic detective work, shoe leather, door knocking, finding witnesses, finding little connections, with technology.

LENTS: Even the most careful killer really can't hide forever. The technology will catch up and new analysis methods become online, and that's why we hold on to evidence for a long time.

GINGRAS: Coming up, the victims' families.

KIM OVERSTREET, AMBER LYNN COSTELLO'S SISTER: This is the last place she was.

(COMMERCIAL BREAK)

[20:53:01]

TIERNEY: Melissa Barthelemy, Megan Waterman and Amber Costello. The investigation of Maureen Brainard-Barnes is ongoing.

UNIDENTIFIED MALE: Each one of these victims was a family member and a loved one. And their void and their loss caused great pain and they did not deserve this. Nobody is deserving of this.

GINGRAS: Allie Pertel's sister Megan Waterman was 22 when she was killed, leaving behind a 3- year-old daughter named Liliana.

ALLIE PERTEL, MEGAN WATERMAN'S SISTER: She loved her daughter so much. She was really kind-hearted, you know.

LORRAINE ELA, MEGAN WATERMAN'S MOTHER: My daughter was Megan Waterman.

GINGRAS: Megan's mother Lorraine held this vigil for her daughter in 2011.

ELA: Megan was a kind, loving, friendly person. Whoever met Megan they would definitely fall in love with her. She just had that kind of heart.

PERTEL: She was a victim truly of her lifestyle, nobody wants to do what they are doing in that role. But that's where she found herself unfortunately

She made mistakes, who doesn't? She didn't deserve this. Nobody deserves this.

GINGRAS: Megan's aunt Elizabeth Meserve told CBS's "48 Hours" that Megan's boyfriend coerced her into prostitution.

UNIDENTIFIED FEMALE: Why did she stay with him?

ELIZABETH MESERVE, MEGAN WATERMAN'S AUNT: Fear. She was afraid he would hurt her family, he would hurt Liliana.

GINGRAS: Megan's daughter was interviewed by "48 Hours" 10 years after her mother was killed.

LILIANA, MEGAN WATERMAN'S DAUGHTER: I would do anything to bring her back, but I can't. And it just like frustrates me so bad.

GINGRAS: Maureen Brainard-Barnes was also a mother when she disappeared. Police say Heuermann is the prime suspect in her case.

KOLKER: She had two kids, a boy and a girl. She had a brother and a sister who she had dinner with every week.

[20:55:03] She had a serious boyfriend. And she had a series of jobs, not just sex work. She was a blackjack dealer and she worked at a home security firm. She was doing whatever she could to make it work.

GINGRAS: Maureen's sister, Melissa, told "48 Hours" she turned to escorting to try to make ends meet.

MELISSA CANN, MAUREEN BAINARD-BARNES' SISTER: From her e-mails I can see how desperate she was to get money to be able to save herself from being evicted.

UNIDENTIFIED FEMALE: And save her son, save custody of her son?

CANN: Yes.

GINGRAS: Melissa spoke to CNN in 2011 after Maureen's body was identified in Gilgo Beach.

CANN: I cannot describe to myself how bad it feels to be, you know, a family member of one of these girls that were found.

GINGRAS: Kim Overstreet's sister was also one of the Gilgo Four. 27- year-old Amber Lynn Costello was last seen in 2010.

OVERSTREET: It's my baby sister. You know, it eats at me every day. It consumed me.

GINGRAS: Like her sister Kim worked as an escort. But she believes Amber was more vulnerable because of her struggles with addiction.

OVERSTREET: By the time she was probably 16 years old up until the day she went she was still fighting it. So, she, you know, she had a -- she had a hard life. She really did.

GINGRAS: CNN took Kim to Amber's home in West Babylon where she was last seen by friends.

UNIDENTIFIED MALE: Are you OK?

OVERSTREET: Yes, it's just hard.

UNIDENTIFIED MALE: Tell me what's going on.

OVERSTREET: This was just the last place she was, you know. And I have been here so many times with her. I just can't believe the one time I'm not with her it happens.

GINGRAS: Amber's residence was just under 40 miles from the home of Melissa Barthelemy in the Bronx. Her body was the first of the Gilgo Four to be found. Melissa was only 24 when she went missing in 2009 after she finally graduated from high school.

BARTHELEMY: She had dropped out of school because she was having a few problems and she got herself back in school. She didn't want a GED. She wanted a diploma. And she went back and got all straight A's and she graduated. GINGRAS: After high school, Melissa moved from her hometown of Buffalo

to New York City.

BARTHELEMY: She thought that she could make a lot more money because she wanted to open her own salon back home and buy a house. And that kind of money wasn't available here.

GINGRAS: Melissa found work quickly in a barbershop and made friends easily while living in the city.

BARTHELEMY: If she had $5 in her pocket and you needed $5 to get something to eat, she'd give you the whole thing.

GINGRAS: Melissa soon found that cutting hair wasn't enough, so she turned to exotic dancing and eventually escorting.

BARTHELEMY: Still hard for me to take it all in because she always knew that she could come home.

GINGRAS: Lynn wanted to make sure Melissa and the rest of the Gilgo Four are remembered for who they were.

BARTHELEMY: It doesn't matter what they did for a living they're still all beautiful girls. And they were very young and they had a lot of life.

GINGRAS: More than anything, though, Melissa's mother wanted justice.

BARTHELEMY: We want to catch this guy. We want to stop him before anymore girls go missing.

GINGRAS: Fourteen years later the police have now said they have the very same fear. That their prime suspect could strike again. They had to act.

TIERNEY: We had the FBI surveilling the defendant. But this individual was a person that continued to patronize sex workers at all hours of the night. He continued to use fictitious e-mail, fictitious identities, burner phones. It was time to take him off the streets.

MILLER: This is the kind of case a prosecutor dreams about. It's an extraordinarily strong case. It combines an incredible amount of circumstantial evidence with technological evidence in terms of cell phones and scientific evidence in terms of DNA.

GINGRAS (on-camera): Is this case over from your perspective?

HARRISON: Not even close. You know, we still have the other six bodies that were recovered on Ocean Parkway. You know, we have some work to do. And this task force is going to stay intact. Is Rex Heuermann connected to these other bodies? Time will tell.

ANTHONY CARTER, SUFFOLK COUNTY DEPUTY POLICE COMMISSIONER: As we continue to gather evidence, anything is possible.

(END VIDEOTAPE)

COOPER: Police are continuing their investigation into the other seven remains found in the Gilgo Beach area. They are asking the public to come forward with any tips or information they may have on these cases.

Thanks for watching. I'll see you next Sunday.