Gilgo Beach serial killer Rex Heuermann told ex-wife he killed 7 of 8 victims at their Massapequa Park home, documentary reveals

Gilgo Beach serial killer Rex A. Heuermann told his ex-wife he killed seven of his eight victims inside their Massapequa Park home shortly before he pleaded guilty, she reveals in a new episode of a documentary series about their lives debuting this week.

Asa Ellerup also says Heuermann told her the eight women he admitted to killing are his only victims, according to a teaser clip released by Peacock Monday.

"I said to him, ‘So Mr. Heuermann, I understand that you are confessing to me on those murders. Can you tell me how many of these women did you kill?,’ " Ellerup says in the teaser. "He said, ‘Eight.’ "

Ellerup goes on to reveal the killings occurred in a room Heuermann kept in the basement.

"All except one," she says at the conclusion of the 90-second teaser.

The fourth and final episode of "Gilgo Beach Serial Killer: House of Secrets" will be available on the streaming service Thursday morning. It is one of two new documentary projects about the killer hitting major streamers this week. "Killing Grounds: The Gilgo Beach Murders" will debut on Amazon Prime Wednesday.

"House of Secrets," from executive producer Curtis "50 Cent" Jackson, arrived on Peacock with three episodes in June. It features exclusive interviews with Heuermann’s family members, who were reportedly paid more than $1 million for the access and to allow the documentary crew into their Massapequa Park house.

"This has been an extremely emotional and painful process for the family to endure and come to terms with the allegations that Rex Heuermann was the Gilgo Beach serial killer," Ellerup attorney Robert Macedonio said in a statement. "Ms. Ellerup would like the focus to remain where it belongs — on the victims and their families, who have suffered immeasurable and lasting losses."

Peacock’s announcement Monday also reveals the participation of the family’s psychotherapist, who shares notes from her conversations with the convicted killer, and former FBI profiler John Douglas in the new episode.

Law enforcement seized a copy of Douglas’ book "Mindhunter" while executing a search warrant of Heuermann’s home following his arrest in July 2023. The Behavioral Analysis Unit Douglas pioneered with the FBI is interviewing the serial killer as part of a plea agreement, his attorney said when he changed his plea to guilty April 8.

The confession brought resolution to a case that has generated worldwide attention since the first victim's remains were found off Ocean Parkway in 2010.

During the plea hearing Heuermann admitted strangling eight women — Melissa Barthelemy, Megan Waterman, Amber Lynn Costello, Maureen Brainard-Barnes, Jessica Taylor, Sandra Costilla, Valerie Mack and Karen Vergata — and dumping their bodies across Suffolk County, including near Gilgo Beach. The crime spree began in 1993 and continued until police discovered some of the remains while searching for a different missing woman in December 2010.

Heuermann has never been charged in Vergata’s death. His plan to admit to her killing was first reported by Newsday the day before he entered his guilty plea. He will be receive multiple life sentences when he is sentenced by State Supreme Court Justice Timothy P. Mazzei on June 17.