Rex Heuermann, the man accused of killing four sex workers and dumping their bodies on Long Island's Gilgo Beach in New York, was indicted Thursday in the slayings of two more women as authorities revealed disturbing new evidence − including a "planning document" allegedly found on Heuermann's computer.

Heuermann, 60, was arraigned in Suffolk County Court in the deaths of Jessica Taylor, 20, whose dismembered remains were first found days after she disappeared in 2003, and Sandra Costilla, 28, whose body was found in 1993. He now faces two additional second-degree murder charges.

"This year has been 21 years since she was taken from us, longer than the chance that she got to be alive," Jasmine Robinson, Taylor's cousin, said at a news conference on Thursday. "I can't express what this day means after waiting and hoping for answers."

"Jessica, my darling daughter, you will never be forgotten," Elizabeth Baczkiel, Taylor's mother, wrote in a statement read by her attorney, Gloria Allred. "You will always be missed. You will forever be in our hearts."

The new charges came just weeks after authorities renewed searches of Heuermann's home in Massapequa Park and a wooded area on Long Island where human remains were found over a decade ago.

Investigators found new evidence, including a document on a hard drive recovered from Heuermann's basement that they believe he used to plan the murders, according to a superseding bail application emailed to USA TODAY on Thursday.

"The task force believes that this is a planning document and it was utilized by Heuermann to methodically blueprint and plan out his kills with excruciating detail," Suffolk County District Attorney Ray Tierney said at a news conference.

What does the 'planning document' tell investigators?

The document lists "supplies," including "saw/cutting tools," and "photo film," and a "DS," which investigators believe stands for "dump site." It also contains a "dispose of the following" section and the note, "hunt too long seen in area too long." Another note says that more sleep and "noise control" would allow for more "play time," which prosecutors say refers to sexual mutilation.

Some notes from the document were sourced from "Mindhunter: Inside the FBI's Elite Serial Crime Unit," a book by retired FBI agent John E. Douglas and author Mark Olshaker about the psychological profiles of serial killers and mass murderers, according to court documents. For example, prosecutors say one note from the document that reads, "look at the painting," references a passage from the book: “If you want to understand the artist (the perpetrator), you have to look at the painting (the victim)."

Tierney said Heuermann referenced the book "not to gain insight into his own behavior or to modify or change it, but rather to use it as a means of improving his methodology and avoid capture by the authorities."

Throughout multiple searches of Heuermann's residence, authorities seized more than 350 electronic devices, according to the bail application.

Tierney said analysis of Heuermann's devices also turned up a collection of "violent bondage and torture pornography" dating back to 1994. "That material was very similar to the condition that the two latest victims were left in," he said.

The initial search of Heuermann's residence also turned up a copy of “The Cases That Haunt Us," a book about famous serial murder cases by the same authors.

Heuermann has pleaded not guilty to all charges

The former New York architect has been in jail since July on charges in connection with the murder of four women – Maureen Brainard-Barnes, 25, Megan Waterman, 22, Melissa Barthelemy, 24, and Amber Costello, 27 – all sex workers whose bodies were discovered on the same strip of highway on Gilgo Beach on Long Island. Their remains were among 11 sets of remains found throughout suburban Long Island in 2010 and 2011.

Michael J. Brown, Heuermann's attorney, told reporters he was not given the time to review the new evidence enough to comment. "It's unfair when you hand somebody something and say, 'OK, here you go, defend it,'" he said.

Heuermann has pleaded not guilty to all the charges. His trial date has not been set.

"He is the same as he was from day one," Brown said. "He's indicated he is not guilty of these charges, and he wants his day in court now."

Fifth victim's skull, hands, arms found near 'Gilgo Four'

Police first found Taylor's body, decapitated and with both arms severed, in Manorville, Long Island, about 40 miles east of Gilgo Beach, according to court documents. Her skull, hands and forearms were discovered eight years later in 2011 as investigators searched the area where the "Gilgo Four" were found.

Prosecutors say Taylor, a sex worker, would "street walk" near Heuermann's office in midtown Manhattan. Evidence showed that Heuermann's family was out of town at the time of her disappearance, according to investigators.

Investigators also linked hair discovered on both Taylor's and Costilla's bodies to Heuermann through DNA testing.

Tierney said investigators had uncovered more information that prosecutors would unveil during the trial.

DNA on pizza box leads to Heuermann's July arrest

Heuermann's arrest in July came more than a decade after the first bodies were discovered on Gilgo Beach in 2010. He was first identified as a suspect in Costello's death in March of 2022 when investigators linked him to a pickup that was reportedly seen by a witness in 2010.

According to an indictment, detectives on the case found credit card payments and phone calls made by Heuermann in the same area where someone used burner phones to contact several of the victims before they disappeared. Prosecutors said Heuermann's Tinder profile, where he went by the name "Andy," had links to the burner phones.

Detectives also found searches on other serial killers and "sex workers, sadistic, torture-related pornography and child pornography" on a burner email account investigators tied to Heuermann, the indictment said.

A key breakthrough in the investigation came the next year, when a surveillance team saw Heuermann throw a pizza box into a trash can outside his office and DNA taken from the crust matched DNA from a hair found on one of the victims.

Days after the arrest, Heuermann's wife Asa Ellerup filed for divorce.

In March, Ellerup's attorney wrote in a statement that she still visits her ex-husband weekly and "believes he is not capable of the crimes he is accused of."

“I will listen to all of the evidence and withhold judgment until the end of trial," Ellerup said in the statement. "I have given Rex the benefit of the doubt, as we all deserve.”

Cybele Mayes-Osterman is a breaking news reporter for USA Today. Reach her by email at [email protected]. Follow her on X @CybeleMO.