RIVERHEAD, N.Y. – Suspected Long Island serial killer Rex Heuermann returned to a New York courthouse Thursday to be charged with killing two more women.

Heuermann was indicted on two new murder charges in the deaths of Jessica Taylor in July 2003 and Sandra Costilla in November 1993.

Authorities also revealed in court records that during their investigation they found a document on Heuermann’s computer they believe was a “planning document” he used to “methodically blueprint and ‘plan out’ his ‘kills,’” with sections about things to remember, problems, supplies, prep work, dump sites and targets.

Police arrested the 59-year-old New York City architect last year in connection with three cold case murders and prosecutors secured an indictment for a fourth victim months later. He made a brief appearance in court Thursday in a suit and handcuffs, and is due back on July 30.

REX HEUERMANN’S FAMILY KEPT GRUESOME PIECE OF EVIDENCE, SOURCE SAYS

The Gilgo Beach murders went unsolved for more than a decade. And the case is broadening.

A task force with state and local investigators pieced together evidence that led them to their “ogre” suspect: an eyewitness description of his green Chevy Avalanche, records from a slew of burner phones, crime scene DNA and a discarded pizza crust.

Taylor’s body was discovered in Manorville, Suffolk County, on July 26, 2003, with her head decapitated, her arms severed, and a tattoo mutilated. Her other remains were found on March 29, 2011, along Ocean Parkway, just east of Gilgo Beach, near where the other Gilgo victims’ remains had been found.

Costilla’s remains were found on Nov. 20, 1993, in a wooded area of Southampton.

In July 2023, police arrested Heuermann outside his Manhattan office and spent nearly two weeks scouring through his home in Massapequa Park, about 20 minutes from where police found the bodies of Melissa Barthelemy, 24; Megan Waterman, 22; and Amber Costello, 27, in 2010.

Prosecutors later tacked on charges for the murder of Maureen Brainard-Barnes, 25, whose remains they found near the others.

Collectively, those women are known as the Gilgo Four because they were found close together and under similar circumstances.

SUSPECTED SERIAL KILLER REX HEUERMANN’S HOME SEARCHED AGAIN

Police uncovered their remains in the brush along Ocean Parkway after another woman, Shannan Gilbert, vanished into the night after placing a panicked 911 call begging for help.

Police found seven other bodies further east along the highway. Most of the deaths remain under investigation. Gilbert was the last one in 2011.

John Ray, attorney for Gilbert’s family, said after Thursday’s court appearance that Heuermann’s notes mentioned Stockholm syndrome, which suggests he held his alleged victims for some unknown time.

“How long did he keep them alive is the big question,” Ray said.

Ray, who said he has evidence that ties Heuermann to Gilbert, said he does not think that any of things listed in the planning document would ever be found.

Police said in 2020 that Gilbert’s death appeared to be an accidental drowning, although her official cause of death is undetermined and a private autopsy conducted by Dr. Michael Baden found evidence of “homicidal strangulation.”

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Another Long Island homicide victim is Valerie Mack, who was dismembered and dumped.

Additional remains of hers were uncovered near the Gilgo victims.

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K-9 units conducted a search in Manorville in April and then served a second search warrant on Heuermann’s house in May.

The prime suspect in Costilla’s death was previously another serial killer, former Manorville carpenter John Bittrolff, who is currently in prison for two other murders.

If Heuermann is responsible for any of the deaths out east, his suspected killing spree would have started years earlier than previously known.

Heuermann has pleaded not guilty to murder charges in connection with the Gilgo Four.