ABC News June 6, 2024

Gilgo Beach serial killing suspect Rex Heuermann charged in 2 more murders, new disturbing details revealed

WATCH: New charges against Rex Heuermann paint a timeline of murders from 1993 to 2010

Disturbing new details were revealed in the Gilgo Beach serial killings case as suspect Rex Heuermann was charged Thursday with the murders of two additional women, bringing his total number of alleged killings to six.

Heuermann was charged Thursday with the 2003 murder of Jessica Taylor, whose remains were found on Long Island in Gilgo Beach and in Manorville, and accused of the 1993 murder of Sandra Costilla, whose remains were found in North Sea, Long Island, in 1993, according to court documents. These developments significantly expand the timeline in the Gilgo Beach case, with the first murder Heuermann is accused of committing now taking place in 1993.

Suffolk County Police Department
Police released this photo of Sandra Costilla.

The architect and father allegedly "meticulously planned and executed six separate murders," Suffolk County District Attorney Raymond Tierney said at a news conference Thursday.

Tierney said the discovery of a digital "planning document" on one of 350 electronic devices seized from Heuermann’s Massapequa Park, New York, home was a "significant impetus" for investigators to return to Heuermann’s house and two locations in eastern Long Island.

Investigators said the planning document contained a checklist of things to do in order to package a body for transport, avoid leaving traces of DNA and other steps. There were notes indicating steps to take "next time," i.e., considering a hit to the face or neck "NEXT TIME," or using heavier rope for the neck, according to court documents.

Howard Schnapp/Newsday RM via Getty Images, FILE
In this July 20, 2023, file photo, police and crime scene investigators continue to go through the home of Gilgo Beach murder suspect Rex Heuermann, in Massapequa Park, N.Y.
MORE: Gilgo Beach: 'Cutting edge' DNA evidence helped link suspect to 4th victim, DA says

Heuermann allegedly wrote about the importance of sleep to not only avoid "PROBLEMS" but also to increase what he referred to as "PLAY TIME," which is believed to be a reference to sexual and mutilation acts perpetrated on victims.

Court documents show he also allegedly had a "post event" checklist, which appeared to be a "checklist of tasks following the 'event' or homicide to avoid apprehension, i.e. ... 'BURN GLOVES,' 'DISPOSE OF PICS' taken of the victim, and 'HAVE STORY SET' (e.g., alibi, story for family upon their return, or law enforcement, should an inquiry be made)."

Spencer Platt/Getty Images
An aerial view of police cars near where a body was discovered in the area near Gilgo Beach and Ocean Parkway on Long Island, April 15, 2011, in Wantagh, N.Y.

Taylor was a sex worker in midtown Manhattan, in the same area where Heuermann worked, and records showed Heuermann was in Midtown the day Taylor disappeared, according to court documents.

Taylor was decapitated and her arms were severed from her torso, officials said. Some of Taylor's remains were found in 2003, but her head, hands and forearm were not located until March 2011, when they were discovered on the same side of the road from where four of Heuermann's other alleged victims had been found just months earlier in December 2010, according to court documents.

John Ray Law via AP, FILE
This photo provided by John Ray Law on July 14, 2023, shows Jessica Taylor, whose remains were found decades ago along on a highway along Gilgo Beach, on New York's Long Island.

Investigators linked Heuermann to Taylor's death in part through DNA from hair recovered from a surgical drape that had been underneath her body, according to a newly unsealed court document.

Investigators also said phone records established that Heuermann's wife and children were out of town when Taylor was killed, "which would have allowed Defendant Heuermann unfettered time to execute his plans for Ms. Taylor, which included the decapitation, dismemberment, and transportation of her remains, without any fear that his family would uncover or learn of his involvement in these crimes," court documents said.

Prosecutors also noted that "Heuermann accessed a Newsday Article entitled, 'Cops Seek Help in IDing Manorville Body,' regarding the discovery of Ms. Taylor's human remains," court documents said.

Pool
Alleged Gilgo serial killer Rex Heuermann, center, inside courtroom at Suffolk County Court in Riverhead on Thursday, June. 6, 2024. His attorney, Michael J. Brown is at left.

DNA also linked Heuermann to 28-year-old Costilla, whose body was found in a wooded area in North Sea, Long Island, in November 1993, prosecutors said.

"Pornographic images accessed by Heuermann ... notably and largely coincide with how" the remains of Taylor and Costilla were found, according to court documents.

James Carbone/Pool/Getty Images
Alleged Gilgo serial killer Rex Heuermann appears before Judge Timothy P. Mazzei with his attorney Michael Brown at Suffolk County Court, Jan. 16, 2024, in Riverhead, N.Y.
MORE: Estranged wife of Gilgo Beach suspect says he's not capable of murders: Lawyer

Heuermann was arrested in July and initially charged with murdering three escorts: Megan Waterman, Amber Costello and Melissa Barthelemy. He was charged in January with the murder of a fourth escort, Maureen Brainard-Barnes.

The remains of all four women were found in 2010 in desolate spots along the ocean near Gilgo Beach. Six additional sets of remains were also found in the area.

Heuermann had previously pleaded not guilty to the four murders.

Phil Marcelo/AP
Suffolk County police stand outside the home of Rex Heuermann, May 24, 2024, in Massapequa Park, N.Y.

Heuermann appeared in court Thursday and his defense attorney said he pleads not guilty to the two new murder charges as well.

He was remanded without bail and is set to return to court on July 30.

Tierney said Heuermann is now the leading suspect in the death of Valerie Mack, whose remains were found in Manorville, near Jessica Taylor’s.

Tierney said investigators would now go back over 30 years worth of crime in Suffolk County and beyond to see what else they might connect Heuermann to.