‘Unintended hero.’ A mother’s quest to find her daughter led to the eventual arrest of suspect in Gilgo Beach serial killings

By Ray Sanchez, CNN

(CNN) — Mari Gilbert did not live to witness the arrest of an architect from Long Island suspected of killing four young women whose remains were discovered in Gilgo Beach more than a decade ago.

But the search for her daughter Shannan Gilbert, who went missing in May 2010, ultimately led Suffolk County police to the bodies of those women, wrapped in camouflaged burlap and discarded along a desolate beachfront parkway.

Shannan Gilbert was 23 when she vanished. Her remains were found in December 2011 in another beach community just down the road. Authorities have said her death may have been accidental and not related to the other killings – a long dormant multiple homicide case known as the “Gilgo Four.”

Mari Gilbert, in the final years of her life, pressured police to take her daughter’s disappearance seriously. She fought tirelessly to ensure that Shannan and the other victims would not be forgotten.

“Mari saw Shannan as an unintended hero because it was Shannan’s disappearance that ironically caused all the others to have been found and, now, to have at least one arrest,” said John Ray, an attorney for the Gilbert family.

Beyond the string of murders and the long elusive hunt for a suspected serial killer is the Hamlet-like tragedy of a troubled family whose legacy may be helping solve what police called “one of the most consequential homicide investigations in the history of Long Island.”

“Who knows what other lives have been saved because of the exposure of all this? And now the arrest of an alleged murderer,” Ray said.

On July 23, 2016, tragedy again befell the family. Mari Gilbert was 52 when she was stabbed hundreds of times with a 15-inch kitchen knife by another daughter, Sarra. She was then bludgeoned to death with a fire extinguisher, according to a court document.

Sarra Gilbert, who Ray said suffered both emotionally and mentally after her sister’s death, was sentenced to a prison term of 25 years to life.

“Mari understood that one way of finding at least a shred of meaning in the loss of her daughter was that her disappearance led to the discovery of those four women several months later, and that without Shannan there would be no case, there would be no search for the killer,” said Robert Kolker, the author of the 2013 book “Lost Girls: An Unsolved American Mystery,” which closely examined the case.

“She understood that very well, and I believe she found some redemption in that idea: that Shannan’s loss helped others learn the truth.”

‘I’m glad I’m still alive to see it’

Shannan Gilbert’s disappearance on May 1, 2010, was followed by years without an arrest, or suspect, or promising leads and – as Kolker put it – “barely a peep from the police or the authorities.”

That is until July 13, 2023, when police arrested Rex Heuermann, an architectural consultant who worked in Manhattan and lived with his wife and children in Massapequa Park, across the bay from where the remains of the women were found, on the southeastern edge of Nassau County.

Heuermann has pleaded not guilty to the murders of Megan Waterman, Melissa Barthelemy and Amber Lynn Costello. In January, he was charged with the murder of a fourth woman, Maureen Brainard-Barnes, who was 25 when she was last seen in July 2007. He also pleaded not guilty in that case.

Heuermann, 60, was indicted on two new murder charges Thursday: second-degree murder in the 2003 death of Jessica Taylor and the 1993 death of Sandra Costilla, according to a bail application.

Taylor’s remains were discovered in Manorville in 2003 and then additional remains along Ocean Parkway on Gilgo Beach in 2011. Costilla’s remains were found in North Sea in 1993 by two hunters who were in the woods, according to the bail application.

He pleaded not guilty to the charges.

“Of all the family members, Mari was the one who got the most out of the police, forced them to do things they otherwise wouldn’t,” Kolker wrote in the new afterword of his book – which was adapted into a 2020 article in New York Magazine. “And she didn’t just make a lot of noise; the experience of fighting on behalf of her daughter Shannan transformed Mari, too.”

Mari Gilbert in 2011 accused police of botching the investigation, which she described as “clownish.” For years, Gilbert and others maintained that investigators dragged their feet because the victims, like Shannan, were sex workers.

“We kept all the cases alive by keeping alive the Shannan Gilbert case,” Ray said. “There’s no question of that at all. The police had entered into a dreamland of waiting it out.”

A major corruption scandal within Suffolk County law enforcement did not help matters.

In 2015, Suffolk County Police Chief James Burke was arrested and accused of beating a man who allegedly broke into his vehicle in 2012 and stole a bag that contained sex toys and porn, and then conspiring to block the FBI investigation into his actions, according to court records.

Burke ultimately pleaded guilty to a civil rights violation and conspiracy to obstruct justice. He was sentenced to 46 months in prison, the records show.

Notably, a day after Burke was arrested, the Suffolk County police deputy commissioner at the time announced the FBI would join the investigation into the Gilgo Beach murders.

Kolker said Mari Gilbert and the other family members meanwhile banded together to become “a powerful force for advocacy.”

“They reminded people that there were real human beings at stake here, that this wasn’t just a Hannibal Lecter movie,” he said.

“But among all the family members, Mari was the one who was the most provocative personality. She was the one who when things started to get quiet would stand up and make some noise and make sure that the police responded.”

The day after Heuermann’s arrest as he left work near the Empire State Building, Gilbert’s second eldest daughter, Sherre, expressed her support for the families of the victims on a Facebook page titled “Praying for Shannan Maria Gilbert.”

The “time, effort, and dedication my mom & I put into this case (wasn’t) wasted… I wished, hoped & prayed for this day. I’m glad I’m still alive to see it,” she wrote.

Kolker, whose book was in 2020 turned into a film for Netflix also titled “Lost Girls,” said: “I think Mari would have been much the same way if she were here. She would have celebrated the arrest and voiced support for the other families.”

‘Some things that we could have done better’

In February 2022, Suffolk County Police Commissioner Rodney Harrison formed a multiagency task force, including state police and the FBI, to revisit the case – an effort that led to Heuermann’s arrest.

Within months investigators made a “significant” discovery that led them to focus on Heuermann, according to the prosecution’s bail application.

Prosecutors said police found a first-generation Chevrolet Avalanche – the same type of truck a witness believed to have been driven by Costello’s killer – registered to Heuermann at the time of the murders.

Investigators later recovered DNA from a pizza crust that was thrown away outside Heuermann’s Manhattan office and linked it to the alleged killer of the Gilgo Four.

After the arrest, Harrison defended the police investigation.

“Since the discovery of the first victim, there has been a lot of scrutiny and criticism regarding how this investigation was handled,” he said.

“I will tell you this, the investigators were never discouraged. They continued and uncovered evidence and followed leads. They never stopped working and will continue to work tirelessly until we bring justice to all the families involved.”

Harrison later told CNN, “There might have been some things that we could have done better but we’re here today and we’re announcing that we’re placing this animal under arrest.”

Last year, Suffolk County authorities announced they had identified another Gilgo Beach murder victim – known as “Fire Island Jane Doe” – as Karen Vergata, a 34-year-old escort from Manhattan who went missing on Valentine’s Day in 1996.

Vergata’s remains were among nearly a dozen sets of human remains found along Ocean Parkway on the South Shore of Long Island between 2010 and 2011, including Shannan Gilbert and the Gilgo Four victims.

Suffolk County District Attorney Ray Tierney told reporters at the time there are “no charges at this time” and investigators continueds to work on the case. Tierney did not link Heuermann to Vergata’s death.

“It’s sort of seems like we’re on the road to getting answers for some of these deaths,” Kolker said. “But there are many, many unsolved murders still in Long Island along the shore… There’s a glimmer of progress now. But along with celebrating what’s happening, I think a lot of people are asking what took so long.”

‘She does not deserve to be forgotten’

Early on the morning of May 1, 2010, Gilbert – who lived in New Jersey – traveled with her driver from Manhattan to meet a man at his home in Oak Beach on Long Island. Gilbert appeared “irrational” at some point and the man contacted the driver, according to a Suffolk County police online summary of the Gilgo Beach homicide investigation. She fled on foot and approached two homeowners in the area before she vanished.

The driver and the man Gilbert visited that morning were investigated and cleared of criminal involvement in her death, according to police.

An analysis by the FBI and a psychiatrist of a 911 call Gilbert made at the time, as well as the circumstances of her disappearance, found that her death was “not consistent with her being the victim of violence or of a violent offender,” according to Suffolk County police.

In the frantic 911 call, Gilbert screamed, “They’re trying to kill me,” according to CNN affiliate WPIX-TV.

The search for her led to the discovery of the other victims – more than seven months after Gilbert’s disappearance. Gilbert’s remains were found in Oak Beach a year later.

In 2016, Mari Gilbert and Ray held a news conference to announce that an independent autopsy on Shannan’s remains found that her death was “consistent with homicidal strangulation” but there was insufficient information to determine a definitive cause of death.

Holding a photo of her eldest child, Mari Gilbert told reporters that day, “This is my daughter Shannan. She was not perfect. No one is perfect. But she was loved. She was cared for. She does not deserve to be forgotten.”

She kept on living ‘despite such terrible loss’

Over the years, Mari Gilbert’s daughters often appeared alongside her at news conferences and vigils for the victims.

But Ray said daughter Sarra was never the same after Shannan went missing and her remains later discovered.

“She was driven mad quite substantially by the death of her beloved sister,” he said. “She looked up to Shannan as, you know, a demigod and she was brokenhearted by what had happened and it was all simmering in that little mind all that time.”

On an afternoon in July 2016, Sarra Gilbert invited her mother to her home. She stabbed Mari Gilbert 227 times, bludgeoned her with a fire extinguisher and sprayed fire extinguisher foam into her mouth, according to a 2021 ruling upholding Sarra’s conviction by the New York State Supreme Court, Appellate Division, Third Judicial Department.

Sherre Gilbert in 2016 wrote on Facebook: “So as a lot of you may know, my mother passed away yesterday. She was murdered by my sister, Sarra who was battling a mental illness for 2 1/2 years. My sister Stevie and I are incredibly devastated beyond words as our mother was the backbone of the family.”

Police responded to a call from one of Sarra’s sisters. Outside the home, Sherre Gilbert told officers that Sarra “called her that morning and told her that she was hearing voices,” the document said.

Inside, police found Mari Gilbert’s body and Sarra smoking a cigarette. In body camera footage played for the jury at trial, Sarra told police in a soft voice, “I killed my mom,” though she later said Gilbert was still alive.

Sarra told police that before the killing she heard voices referring to her mother as the “devil” and a “bad God” and directing her to kill Gilbert, according to the document.

“Mari loved her daughter,” Ray said. “She went to her death … knowing when she was going to that house that she was in danger.”

Sarra’s younger sister, Stevie Smith, testified for the prosecution at trial, saying that Sarra “had a strained relationship with the victim, who had obtained custody of defendant’s son following a February 2016 incident in which defendant drowned a puppy in front of the child,” the document said.

The prosecution maintained that Sarra plotted the killing after her mother had Sarra arrested months earlier for killing the puppy. The defense argued that Sarra harbored delusions fueled by years of abuse and mental illness. A forensic psychologist testified for the defense that Sarra suffered from “acute symptoms of schizophrenia at the time of the killing.”

“We have no doubt that defendant suffers from a debilitating mental illness that blurs the lines of fiction and reality, and we are certainly sympathetic to the difficult life circumstances she has endured,” the ruling said.

“The proof, however, reasonably supports the jury’s finding that, at the time of the killing, defendant had the substantial capacity to know and appreciate both the nature and consequences of her conduct and that such conduct was wrong.”

Kolker, in the 2020 afterword to his best-selling book, wrote: “Mari’s life, transformed by the death of one daughter, had been ended by another.”

“She was not a perfect person and she was a confrontational person,” Kolker said in an interview. “But in her final years, she became the caregiver for another sick daughter of hers. And her tragic death was awful. But everyone I talked to who knew her well said that in her final years she had grown as a person and really found a way to keep on living despite such terrible loss.”

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CNN’s Eric Levenson, Brynn Gingras and Alisha Ebrahimji contributed to this story.