Gilgo Beach killings: How Rex Heuermann's 'manifesto' became road map for investigators 

Suspected Gilgo Beach serial killer Rex A. Heuermann thought he had long deleted what prosecutors called a “manifesto” on how to kill and avoid detection, a two-page document littered with bone-chilling references to a “dump site” and burning clothes.

Under the ominous subheading of “body prep,” prosecutors said Heuermann listed “remove head and hands” and “package for transport.”

The existence of the “manifesto” was publicly disclosed Thursday as Heuermann was arraigned on two more murder counts. Prosecutors say evidence, including DNA, links Heuermann to victims Jessica Taylor, a 20-year-old sex worker and Poughkeepsie native who lived in Manhattan, and Sandra Costilla, a Queens resident who was 28 when she was killed and her body dumped in a field in North Sea.

Suffolk County District Attorney Ray Tierney on Friday called the “planning document” a major break in the case, telling Newsday in an exclusive interview that its contents prompted a second search of Heuermann’s home in Massapequa Park and the woods in Manorville where three of the victims were found.

The Microsoft Word document, created in 2000 and typed in all caps, was a “planning document” used by Heuermann to “methodically 'blueprint' and 'plan out' his 'kills,'” prosecutors said in a bail letter as part of a superseding indictment charging Heuermann with the killings of Costilla and Taylor, bringing the number of women whom Heuermann has been charged with killing to six.

“The Gilgo Homicide Task Force members believe that the totality of circumstances surrounding the HK Planning Document, including Heuermann's attempt to delete its existence, points to it as Heuermann's self-education and 'homework' on the topic of carrying out serial, sexual murder,” prosecutors said in the bail letter.

It was last July, after Heuermann was arrested outside the Fifth Avenue office of his midtown Manhattan architectural firm and charged in the killings of Melissa Barthelemy, Megan Waterman and Amber Costello, that authorities found the hard drive during a two-week-long search of Heuermann's home. Heuermann was later charged with killing Maureen Brainard-Barnes, who along with Barthelemy, Waterman and Costello are known as “The Gilgo Four.”

With mountains of other potential evidence to process from the search of the home and two nearby storage facilities, authorities recovered the document, which was thought to have been deleted by Heuermann, from a hard drive found in the basement only recently — on March 7 — during a computer forensic extraction method called “file carving.”

Tierney on Thursday identified the 60-year-old former architect, who has been living in virtual isolation in the Suffolk County Jail since his arrest July 13, as a suspect in the killing of another Gilgo Beach victim — Valerie Mack, a 24-year-old New Jersey woman who disappeared in October 2000.

The prospect of a suspect indicted on six of the killings was almost unthinkable in the years since authorities found the first remains on Dec. 11, 2010, near Gilgo Beach.

Police had been searching for Shannan Gilbert, a New Jersey woman who was working as an escort and had disappeared after seeing a client in nearby Oak Beach in May 2010. In the following months, the remains of 10 people were found — eight women, one man and a female toddler. Gilbert’s remains were later found, but authorities ruled her death accidental.

Until Heuermann's arrest last year, the mystery of who killed 10 people — mostly sex workers — and dumped their bodies along Ocean Parkway had confounded federal, state and local investigators.

With the indictment of Heuermann in the killing of Costilla, who had not until recently been identified as a possible Gilgo Beach victim, the timeline of the case has broadened significantly. The other five victims were killed from 2007 to 2010, but Costilla was killed sometime in November 1993, suggesting that Heuermann began his alleged killing spree much earlier. On Friday, Tierney said there was anecdotal evidence that Costilla was engaged in sex work.

Their killings are detailed in the bail letter unveiled last week.

Two hunters discovered Costilla’s remains in a wooded area of Southampton on Nov. 20, 1993. A native of Trinidad and Tobago, she was living on Long Island and in Queens and Brooklyn before her disappearance and killing.

Costilla was found lying on her back with her arms outstretched over her head, and her shirt was pulled up over her torso and head, exposing her breasts, authorities said. Her naked legs were spread apart. She had several “sharp force” injuries to her face, torso, breasts, left thigh and vaginal area, authorities said. Three hairs were recovered from her remains — one found on her right arm and two others from tape-lifts of two shirts that were above her head.

Those hairs were earlier tested against the DNA of convicted killer John Bittrolff, long suspected in Costilla’s killing, but he was excluded as a match.

Recent DNA testing comparing Heuermann’s mitochondrial and nuclear profiles to the hairs could not exclude Heuermann as the provider of the hairs found on Costilla’s body.

“It is significant that two forensic laboratories have now independently determined that male hair recovered from the mutilated remains of Sandra Costilla is substantially more likely to have derived from a personal genetically identical to defendant Heuermann’s mitochondrial and nuclear profiles,” prosecutors said in the bail letter.

Further testing showed, according to prosecutors, that another hair found on Costilla’s remains “shares a common base at all compared positions” with a DNA sample provided by a woman who had lived with Heuermann before Costilla’s disappearance and killing. The woman, who authorities referred to only as “witness #3” in the bail letter, said she could not be excluded as the contributor of the hair found on Costilla.

That woman, whose relationship to Heuermann at the time has not been publicly shared, had been living with Heuermann since 1991 and moved out of their shared residence in September 1993 — about two months before Costilla disappeared and was killed, prosecutors said. Heuermann’s late mother had moved out of the home before the woman, prosecutors noted, without giving a time frame on the mother’s cohabitation with her son.

Prosecutors noted that Heuermann would have been living alone at the time Costilla was killed, giving him “unfettered time to execute his plans” without worrying about anyone coming home to discover a crime in progress.

It's a theme that prosecutors have said runs through Heuermann’s alleged killing spree: Heuermann’s family was always vacationing out of state when he allegedly committed the killings. In the case of Taylor, prosecutors said, phone records and other documents indicate that Heuermann’s now-estranged wife Asa Ellerup and children were vacationing in Vermont when the young woman was killed.

Someone walking a dog found Taylor’s remains on July 26, 2003, just west of Halsey Manor Road in Manorville and called 911. Lying on her back with her legs bent beneath her, Taylor was decapitated and both her arms had been severed below her elbows. A tattoo on Taylor’s torso had been “severely obliterated by a sharp object,” prosecutors said, adding that they believe that act, along with the dismemberment of her body, had been done by Heuermann to “inhibit” authorities from positively identifying her remains.

It wasn’t until some eight years later — on March 29, 2011 — that authorities found Taylor’s skull, hands and forearm along Ocean Parkway, just east of Gilgo Beach. Her remains were located less than a mile from where the remains of the Gilgo Four were discovered.

Taylor was last heard from on July 21, 2003 — five days before her partial remains were discovered. Police interviewed a witness who said on July 25, 2003, at about 10:30 p.m., they had seen a dark-colored Chevrolet pickup backed into the same wooded area where Taylor’s remains were later found.

Heuermann had owned a dark green 2002 Chevrolet Avalanche pickup during that time, investigators have said. And it was key to Heuermann’s initial arrest.

A New York State Police investigator assigned to the Gilgo Beach Task Force, using a database that can search for vehicles by make and model, first identified Heuermann as the owner of an Avalanche and a potential suspect on March 14, 2022.

A witness in Costello’s disappearance — her West Babylon roommate — also described to police a similar vehicle being driven by a man who was seen with Costello shortly before she was last seen alive.

Costello got a call from a burner phone purportedly used by Heuermann on Sept. 1, 2010, authorities have said. A man investigators think was Heuermann, described by the witness as appearing like an “ogre” and seeking a paid sexual liaison, came inside the house, but she and others there executed a ruse to take his money, authorities said.

A man posing as her boyfriend showed up and the client said he was only her friend and left. But that same prospective customer contacted Costello the next night and she left with him — the witness telling authorities he saw the dark-colored Chevrolet Avalanche drive away from the home. That was the last time she was seen alive, authorities said.

Police did not appear to act on the witness statements at the time in either sighting of the distinctive-looking vehicle.

After Taylor’s partial remains were found, authorities said, Heuermann searched online for a new Chevrolet Avalanche in bright blue and white and attempted to delete the search.

DNA testing, according to prosecutors, links Heuermann to Taylor’s killing. Heuermann cannot be excluded as the contributor of a male human hair that was recovered from a surgical drape found under Taylor's remains, although 99.96% of the North American population can be, the bail letter said, adding that DNA analysis conducted by two separate labs had reached similar conclusions.

Heuermann is not charged in the killing of Valerie Mack, a sex worker who went missing in 2000, but for the first time Thursday, authorities linked Heuermann to her killing, noting that an analysis of Heuermann's electronic devices revealed a significant collection of violent, bondage and torture pornography, dating to 1994.

The images showed various abuse and mutilation that prosecutors said “notably and largely coincide with how the remains of Sandra Costilla, Jessica Taylor, and Valerie Mack were discovered,” the bail letter reads.

Authorities found Heuermann’s extensive porn collection after seizing more than 350 electronic devices from his home after he was arrested last year.

The HK Planning Document was among the items that piqued prosecutors’ interest. It prompted authorities to search multiple wooded areas in the Manorville area in April, though no new remains were found.

Prosecutors have studied the document and laid out their theories of what it all means. The document lists “finger prints and gloves” and “hair & fiber” as “problems.” Prosecutors said that section of the document appears to be a guide to avoiding apprehension. A section on “supplies,” which lists tarps/drop clothes, medical gloves and saw/cutting tools, are the supplies needed to carry out the killings, prosecutors said.

In another section, Heuermann wrote “remove ID marks,” which prosecutors argue is consistent with Heuermann’s alleged attempt to obscure Taylor’s tattoo. The document’s “body prep” section, which also notes to “remove head and hands,” clearly relates to the condition of Taylor and Mack’s remains, as both victims were decapitated and dismembered at their arms below their elbows, prosecutors said.

Some of the HK Planning Document has origins in the 1996 book written by former FBI special agent and profiler John Douglas entitled “Mind Hunter,” which explored serial killer profiling, prosecutors said, specifically graphic passages on sexual torture.

When authorities searched Heuermann’s home after his arrest, they found another of Douglas’ books: “The Cases That Haunt Us.”

By Nicole Fuller

nicole.fuller@newsday.com@NicoleFuller

Nicole Fuller is Newsday's senior criminal justice reporter. She began working at Newsday in 2012 and previously covered local government.