Shannan Gilbert's disappearance led authorities to the Gilgo Beach serial killer

Shannan Gilbert disappeared on May 1, 2010, after visiting a client she met through Craigslist in the Oak Beach community on Long Island, NY

On the night of her disappearance, she made an urgent call to 911.

“Someone is after me,” she told an operator before fleeing the customer's home around 5 a.m. “Someone is after me – please.”

Gilbert, 23, ran to an elderly neighbor's home, knocked on the door and asked for help before falling down the stairs and running away. The elderly neighbor called 911, as did another neighbor, who told police she was afraid to let Gilbert into her home.

But when police finally dispatched officers, Gilbert was nowhere to be found.

Her disappearance sparked a search that led to the discovery of four bodies in December 2010 – Melissa Barthelemy, Amber Costello, Megan Waterman and Maureen Brainard-Barnes. All four women, like Gilbert, worked as online escorts and had disappeared between 2007 and 2010. (Further searches found the skeletal remains of seven more people, including a toddler.)

Maureen Brainard Barnes; Melissa Barthelemy; Megan Waterman; Amber Lynn Costello.

Suffolk County Sheriff's Department; Barthelemy family; Suffolk County Sheriff's Department (2)

The search for the suspected Gilgo Beach serial killer remained fruitless for more than a decade until authorities linked 60-year-old architect and father of two Rex Heuermann to the murders of Barthelemy, Costello, Waterman and Brainard-Barnes through DNA evidence and phone calls in July 2023. He has since been charged in connection with their murders.

On June 6 of this year, Heuermann was charged with double murder in connection with the deaths of Sandra Costilla in 1993 and Jessica Taylor in 2003.

“Shannan will be remembered as the girl whose death exposed the truth and the killer,” John Ray, attorney for the Gilbert family, tells PEOPLE. “Shannan's case forced authorities to finally follow the evidence that was there for the other girls. Shannan kept the pressure on all these years, even though she was dead.”

I am Gilbert.

AP Photo/Seth Wenig

What happened to Shannan Gilbert?

A year after the remains of Barthelemy, Costello, Waterman and Brainard-Barnes were found, Gilbert's skeletal remains were discovered on December 13, 2011, hidden deep in the overgrown brush of Gilgo Beach, near the gated community of Oak Beach where she was last seen.

Gilbert's mother, Mari, has been vocal in her criticism of the police's handling of her daughter's case, insisting that Shannan's death was a murder. (Tragically, Mari was stabbed more than 100 times by her other daughter, Sarra, in July 2016.)

As part of her commitment, Mari commissioned the famous forensic pathologist Michael Baden to perform an autopsy on Shannan's remains.

Baden concluded that Gilbert's death was the result of strangulation, and considered that damage to a small bone in Gilbert's throat may have indicated that it had been broken during the murder.

Rex Heuermann.

Suffolk County Sheriff's Office

Want to stay up to date with the latest crime coverage? Sign up for PEOPLE's free True Crime newsletter to get breaking crime news, ongoing court coverage and details of intriguing unsolved cases.

Mari also fought for access to the 21-minute tape of Gilbert's 911 call before her death. In 2022, police released the chilling tape in which Gilbert said, “Someone is after me.”

However, the details of her disappearance remain unclear. Police have long suspected that Gilbert somehow got lost in the inhospitable swamp and died accidentally – either from hypothermia or drowning.

At a press conference in 2022, then-Police Commissioner Rodney Harrison said the FBI's Behavioral Sciences Division had evaluated both Gilbert's case and the 911 call.

“Based on the evidence, facts and totality of the circumstances, the prevailing opinion is that Shannan's death, while tragic, was not a murder and most likely not a crime,” said Harrison, who will step down at the end of December 2023.

Today, the Suffolk County Police Department still claims Gilbert's death was “an unfortunate accident,” but “the agency will continue to evaluate any information the public may have to determine a definitive cause of death.” [Gilbert’s] case,” says the ministry’s website, which has since been taken offline.

Ray says he still believes Gilbert was murdered and will continue to search for answers about what happened to her. “It's not over,” he says. “We're going to keep the pressure on the police and the prosecutor as much as we can.”

Anyone with information regarding Shannan Gilbert is asked to contact Crime Stoppers at 1-800-220-TIPS.