Revealed: The shocking truth about Mari Gilbert’s death that Netflix doc Gone Girls left out

Netflix’s new true crime doc Gone Girls: The Long Island Serial Killer dives into the horrifying Gilgo Beach murders, but it conveniently leaves out one massive detail: Shannan Gilbert’s mother, Mari Gilbert’s death. She was brutally murdered before suspect Rex Heuermann was even arrested.

Wait, what happened?

via Netflix

The documentary, which premiered on March 31, follows Mari Gilbert’s relentless fight for justice after her daughter Shannan went missing in 2010. Shannan’s case ultimately led to the discovery of multiple victims, exposing the work of an active serial killer. But while the doc repeatedly references Mari’s efforts, it never mentions that she was killed in 2016—seven years before Heuermann’s arrest.

Mari spent years trying to prove that Shannan was also a victim of the Gilgo Beach killer. Police ruled Shannan’s death an accident, but Mari refused to accept that, believing her daughter was murdered.

“She would still be campaigning to have Shannan’s death ruled a homicide,” journalist Robert Kolker, an expert on the case, said in the documentary. “And she would not be convinced that Shannan’s death was disconnected from the others.”

So how did Mari Gilbert die?

In 2016, Mari was stabbed 227 times and beat to death with a fire extinguisher—by her own daughter, Sarra Gilbert. Sarra, who had struggled with severe mental illness, was later sentenced to 25 years to life in prison.

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Mari’s other daughter, Sherre Gilbert, confirmed the news at the time. She wrote on Facebook, “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 two and a half years. My sister Stevie and I are incredibly devastated beyond words as our mother was the backbone of the family.”

The Gilgo Beach case is far from over

Shannan disappeared in 2010, prompting investigators to search the area. During their search, they discovered multiple bodies, including the Gilgo Four: Megan Waterman, Melissa Barthelemy, Amber Costello, and Maureen Brainard-Barnes. The case went unsolved for over a decade until police arrested Heuermann in 2023. He has been charged with multiple murders but continues to deny all accusations.

Gone Girls: The Long Island Serial Killer is available on Netflix. For all the latest Netflix news, drops, quizzes and memes like The Holy Church of Netflix on Facebook.