Inside the Gilgo Beach murders: How 'meticulous' Rex Heuermann tried to plan the 'perfect crime'

Admitted Gilgo Beach, New York, serial killer Rex Heuermann confessed to the murders of eight women last week, bringing resolution to a 17-year killing spree that terrorized Long Island.

"If I could speak to Rex face-to-face, I would tell him that he has no heart, no soul, he is a monster," Liliana Waterman, whose mother, Megan Waterman, was among the victims, told ABC News.

ABC News Studios' "IMPACT x Nightline: The Monster at the Beach" is streaming on Hulu.

Here's a look inside the infamous case:

<h3>Targeting and killing sex workers</h3>

Heuermann used an alias to communicate with and target sex workers, prosecutors said. From 1993 to 2010, he strangled his victims and dumped most of their bodies near Long Island's Gilgo Beach, according to prosecutors.

All the while, prosecutors said the New York City architect hid in plain sight, living on Long Island with his wife, daughter and stepson.

Heuermann "walked among us, play acting as a normal, suburban dad, when in reality, all along, he was obsessively targeting innocent women for death," Suffolk County District Attorney Ray Tierney said at a news conference last week.

<h3>Heuermann's 'meticulously planned' crimes </h3>

Prosecutors said Heuermann -- who amassed an extensive collection of torture pornography and kept newspaper and magazine clippings about the Gilgo Beach killings -- "meticulously planned" his crimes.

He kept a list of supplies, locations of "dump sites" and reminders for the future like to "consider a hit to the neck next time," prosecutors said.

Heuermann allegedly wrote about the importance of sleep to not only avoid "PROBLEMS" but also to increase what he referred to as "PLAY TIME," which is believed to be a reference to sexual and mutilation acts perpetrated on victims, court documents said.

He also allegedly had a "checklist of tasks following the 'event' or homicide to avoid apprehension, i.e. ... 'BURN GLOVES,' 'DISPOSE OF PICS' taken of the victim, and 'HAVE STORY SET' (e.g., alibi, story for family upon their return, or law enforcement, should an inquiry be made)," court documents said.

"He's getting off on the planning," forensic psychologist Rachel Toles told ABC News. "He's learning from past mistakes and he wants to make sure that he's correcting his errors, so that he maybe one day will get to the perfect crime."

<h3>Shannan Gilbert and the Gilgo Four </h3>

In May 2010, sex worker Shannan Gilbert fled from a client's house near Oak Beach, and she made a 23-minute-long, frantic 911 call in which she screamed, "there's somebody after me ... they're gonna kill me!"

Police searched for Gilbert for months, and in December 2010, investigators found remains they assumed were Gilbert's -- but the remains were actually of another woman, Melissa Barthelemy.

Days later, police searching the area recovered the remains of three more women -- Megan Waterman, Maureen Brainard-Barnes and Amber Costello -- and with Barthelemy, they became known as the "Gilgo Four."

Investigators then started discovering additional human remains elsewhere on Long Island that were similar to the "Gilgo Four." Gilbert's remains were found in December 2011 -- her death is later ruled as an accidental drowning.

<h3>The 8 women</h3>

For years, the Gilgo Beach victims' families waited in agony for answers about what happened to their loved ones, many of whom were working as escorts when they vanished.

"Megan thought nothing would happen to her," said Amanda Gove, whose 22-year-old sister Megan Waterman went missing in June 2010.

"She was only doing this temporarily," Gove said. "And less than a month later, she was gone."

"They were human beings, with aspirations and hope for a better future for themselves," said Melissa Kahn, whose 25-year-old sister Maureen Brainard-Barnes vanished in 2007. "They have families who love and miss them."

Melissa Barthelemy, 24, went missing in July 2009, and that year, her sister, Amanda Funderburg, reported receiving several taunting phone calls that were believed to be from the killer, according to authorities.

"Why would a person like to do this, taunt psychologically?" Toles said. "... There's an element, again, of control, and the element of torture."

<h3>The arrest and the confessions</h3>

The murders went unsolved for years, until 2022, when agencies including the FBI and New York State Police joined local investigators to create the Gilgo Beach Task Force.

Investigators first identified Heuermann as a suspect in 2022 through his Chevrolet Avalanche, a distinctive pickup truck purchased on Long Island. From there, prosecutors said they compiled DNA from a hair lifted from burlap used to wrap some of the victims and from pizza crust in the trash outside Heuermann's Manhattan office.

Heuermann was arrested in 2023, and he went on to plead not guilty to killing seven women: Waterman, Barthelemy, Brainard-Barnes, Amber Costello, Sandra Costilla, Valerie Mack and Jessica Taylor.

He was set to go on trial in September, but on April 8, Heuermann appeared in court and admitted his guilt in all seven killings between 1993 and 2010. He also confessed to an eighth: the 1996 murder of Karen Vergata. 

"It's just been a heavy weight, not knowing exactly who did it, how it happened, not knowing if I could walk past him someday and not know that that was him," Megan Waterman's daughter, Liliana Waterman, told ABC News in a new interview. "Hearing him admit that he killed my mom and all those other girls, it definitely felt like a weight had been lifted off of me."

"There's definitely some things that I want to know more about," she added. "... Things like, why did he choose her? Where did all this happen? How did all of this happen?"

<h3>'Insight' for the FBI</h3>

Heuermann, 62, has agreed to serve three consecutive life sentences followed by four consecutive sentences of 25 years-to-life. His sentencing is set for June 17.

As part of the plea arrangement, prosecutors said he must cooperate with the FBI's Behavioral Analysis Unit.

Tierney, the DA, told ABC News that cooperating is "very important."

"I think [the FBI is] going to, hopefully, gain insight into him, his motivations, you know, what created this need or desire in him," he said. "And hopefully we'll gain insight, you know, for cases going forward."

And for Liliana Waterman, who was 3 years old when her mother, Megan Waterman, went missing, going to a park near her home in Maine makes her still feel connected to her mom.

"Some of my favorite things to do with her when I was younger was go to the park," she said. "I remember when she first went missing, I would always just ask when she was gonna come back, take me to the park. So it's nice to come here and just feel like she's with me."