Alleged Gilgo Beach serial killer Rex Heuermann better sleep with one eye open.

Fellow Suffolk County inmate Philip Walker, in an exclusive jailhouse interview with The Post, warned, “I don’t think people would be too happy if he was in population. I don’t think it would be good if he was moved into population. I could see someone doing something to him.”

The inmate was referring to “general population” cells in Suffolk County Correctional Facility in Riverhead, LI. Heuermann, 59, has been kept away from other prisoners in the jail and remains on suicide watch in an isolated cell.

Heuerman was charged last week in the murders of three sex workers, and investigators are working to find links to at least six other bodies found at Gilgo Beach.

Walker, 56, has been in custody at Riverhead on second-degree murder charges since July 3, after allegedly stabbing 63-year-old housemate James Vaughn to death in a motel in Shirley, LI.

But the accused killer says Heuermann’s alleged murders are unforgivable.

“Crimes against women and girls, especially killing them, is frowned upon here. A lot of us have sisters, daughters, mothers. No one likes guys who did crimes like that,” said Walker, wearing a navy jumpsuit.

He continued: “Most people in here are from Long Island” and familiar with the Gilgo Beach murders.

Walker has yet to see Heuermann because all inmate movement is halted when he’s moved around the 840-bed facility.

Who is Gilgo Beach serial killer suspect Rex Heuermann?

A suspected serial killer has been arrested over the notorious Gilgo Beach murders in Long Island, The Post can confirm.

Rex Heuermann, 59, a married dad of two and architect at a New York City firm, has a home on 1st Avenue in Massapequa Park, sources told The Post.

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His arrest is tied to the “Gilgo Four,” four women — Melissa Barthelemy, 24, Megan Waterman, 22, Amber Lynn Costello, 27, and Maureen Brainard-Barnes, 25 — found wrapped in burlap within days of each other in 2010. 

The body of Barthelemy was first found along Ocean Parkway on Dec. 11, 2010, sparking fears of a serial killer in the area.

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By spring 2011, the number of bodies had climbed to 10, including eight women as well as an unidentified man and toddler.

Heuermann’s arrest comes after Suffolk County’s new police commissioner created a special Gilgo Beach Homicide Investigation Task Force in February 2022.

“Everything shuts down when they move him to the yard, medical, whatever. Over the speakerphone, they said, ‘Stop all inmate movement,’” Walker said, adding this happens about twice a day. 

Who were the Gilgo Beach victims?

Suspected serial killer Rex Heuermann — a New York City architect and married dad of two — was arrested in connection with the long-unsolved Gilgo Beach murders. The arrest is tied to the so-called “Gilgo Four,” women found wrapped in burlap within days of each other in late 2010.

The years-long investigation that led to the arrest revolved around the discovery of more than 10 sets of human remains along Ocean Parkway near Gilgo Beach in Suffolk County between December 2010 and April 2011.

Most victims were petite female sex workers with green or hazel eyes. But there were also two exceptions: a 2-year-old girl and a young Asian man.

Melissa Barthelemy, 24

• Barthelemy was a sex worker who lived in the Unionport section of the Bronx and dreamed of one day opening her own beauty salon. She was last seen alive in her basement apartment on Underhill Avenue on July 12, 2009. Heuermann was charged for Barthelemy’s murder in July 2023.

Maureen Brainard-Barnes, 25

• Brainard-Barnes was living in Norwich, Connecticut. She went missing after taking an Amtrak train from New London, Connecticut, to Grand Central Terminal in Manhattan on July 6, 2007. Her remains were found in December 2010. Heuermann was charged for Brainard-Barnes’ murder in January 2024.

Amber Lynn Costello, 27

• Costello, 27, was a sex worker and heroin addict who lived in West Babylon, New York, at a home with a woman and two men. She advertised on Craigslist and Backpage to support her and her roommates’ drug habits. Costello was found on December 13, 2010, after having been last seen leaving her home September 2, 2010. Heuermann was charged for Costello’s murder in July 2023.

Megan Waterman, 22

• Waterman, a 22-year-old mom of one, was last seen on June 6, 2010. She lived in Scarborough, Maine, and earned a living as an escort. She was last seen by her family boarding a New York-bound Concord Trailways bus in Maine. Her body was found on December 13, 2010, on the north side of Ocean Parkway, near Gilgo Beach. Heuermann was charged for Waterman’s murder in July 2023.

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Jessica Taylor, 20

• Remains belonging to Jessica Taylor, a 20-year-old woman working as an escort in New York City, were found in a wooded area in Manorville on July 26, 2003. Her additional remains — initially labeled “Jane Doe No. 5” — were discovered on March 29, 2011, along Ocean Parkway.

Valerie Mack, 24

• Valerie Mack was 24 years old and living in Philadelphia when she went missing. She worked as an escort, using the alias “Melissa Taylor.” Relatives last saw Mack in the spring or summer of 2000 in Port Republic, New Jersey, but she was never reported as missing to the police. Her partial skeletal remains were found in Manorville in September 2000 but were initially known as “Jane Doe No. 6.” More bones were found on April 4, 2011, along Ocean Parkway.

Unidentified Asian man

• The skeletal remains of a yet-to-be-identified Asian man were found along Ocean Parkway on April 4, 2011. It is estimated that the man was between 17 and 23 years old at the time of his death. He was approximately 5 feet 6 inches tall with bad teeth.

‘Peaches’ and her daughter

• An African American woman’s partial remains were discovered in Hempstead Lake State Park back in 1997, and she had become known as “Peaches” because of a bitten tattoo of a peach on her left breast. On April 4, 2011, police uncovered the remains of a toddler, who was about 2 years old at the time of her death. DNA testing confirmed that one of the skeletons was that of the 2-year-old girl’s mother, “Peaches.”

Karen Vergata

• A victim previously referred to as Jane Doe No. 7 has been identified as 34-year-old Manhattan woman Karen Vergata. Vergata is believed to have disappeared around Feb. 14, 1996; two months later, her legs were found in a plastic bag at a park near Fire Island’s Blue Point Beach. At the time of her disappearance, Vergata was believed to have been working as an escort. Two sets of Vergata’s remains were identified in August 2023.

Shannan Gilbert, 23

• Gilbert was a Craigslist escort who lived in Jersey City, traveled with her driver Michael Pak from Manhattan to meet a client, Joseph Brewer, at his home in the Oak Beach Association on the morning of May 1, 2010. She spoke with two neighbors before disappearing. Her body was discovered in a marsh near Oak Beach — about half a mile from where she was last seen alive — on December 13, 2011.

Jessica Taylor, 20

• Taylor, a 20-year-old woman working as an escort in New York City, were found in a wooded area in Manorville on July 26, 2003. Her additional remains — initially labeled “Jane Doe No. 5” — were discovered on March 29, 2011, along Ocean Parkway.

Sandra Costilla

• Costilla was murdered in 1993 but had not been included among the so-called Gilgo Beach victims — until now. Investigators suspected convicted serial killer John Bittrolff in Costilla’s death, but he was never charged in her slaying — which remains one of several unsolved Long Island murders.

“We all know it’s for him,” Walker said.