Read PEOPLE's 2023 Cover Story on Alleged Gilgo Beach Serial Killer, Who's Now Charged with 6 Murders

Rex Heuermann is now accused of murdering six women

Editor's note: Rex Heuermann, the alleged Gilgo Beach Serial Killer, was charged on Thursday, June 6, with two additional murders, meaning he's now accused of killing six women.

Suffolk County, N.Y., prosecutors accused Heuermann Thursday morning of murdering Sandra Costilla in 1993 and Jessica Taylor in 2003.

Heuermann, who worked as an architect in Manhattan, is already facing murder charges in the deaths of Megan Waterman, Melissa Barthelemy, Amber Costello and Maureen Brainard-Barnes. All four women worked as online escorts and disappeared between 2007 and 2010.

Here is PEOPLE's July 2023 cover story following Heuermann's arrest.

On a hot, humid late-summer night in 2010, Amber Costello, 27, called her roommate from the locked bathroom of their rented cottage in West Babylon, N.Y., on Long Island. She was terrified. Costello, a sex worker, had been dancing for a client when he’d threatened to rape her, she said. Her roommate raced home and burst through the door ready to take a swing at anyone inside, only to find a hulking man in the living room who barely flinched. “It was like fighting Frankenstein,” the roommate says. As the man drove away in a first-generation Chevy Avalanche, he uttered a chilling admonition: “You don’t know who you’re f---ing with.” Says Costello’s roommate, who has asked not to be identified by name: “He had the blankest look on his face.”

Shortly after, on Sept. 2, 2010, Costello left her home and was never seen again, yet her roommate never forgot the man or his haunting expression. And on July 14, 2023, when a picture of architect and twice-married father of two Rex Heuermann, 59, of nearby Massapequa Park, flashed across the news, “I said, ‘That’s the Frankenstein dude. That’s him.’”

Police in New York’s Suffolk County say they have finally caught the deadly predator known as the Long Island Serial Killer, believed to have murdered at least 3 and, by some estimates, as many as 18 victims over a decade. Heuermann is charged with three counts each of first- and second-degree murder for the killing of Costello, Melissa Barthelemy, 24, an aspiring hair salon owner who went missing in 2009, and Megan Waterman, 22, who vanished in 2010. Charges in the murder of Maureen Brainard-Barnes, 25, a mother of two who disappeared in 2007, are likely pending, say prosecutors. (Heuermann has pleaded not guilty on all counts.)

Authorities point to the work of an interagency task force—made up of FBI agents and state and local police—put together in early 2022 for identifying Heuermann as a suspect in March 2022 and working fastidiously to build a case. “Rex Heuermann is a demon that walks among us, a predator that ruined families,” Suffolk County Police commissioner Rodney Harrison said at a July 14 press conference. “If not for the members of this task force, he would still be on the streets today. However, even with this arrest, we’re not done.”

***

Neighbors on First Avenue in the usually sedate village of Massapequa Park who woke up on the morning of July 14 to find an army of investigators searching Heuermann’s ranch-style house—reportedly his childhood home—are in shocked disbelief that an accused serial killer had lived in their midst. “He was a recluse,” says Michael Musto, who lives a few doors down from Heuermann. Musto’s sister would try to speed her pace up when walking the dog past the house, with its sagging front porch and dilapidated wood shingles. “She felt uncomfortable,” Musto says. “She had a sixth sense that she picked up on.”

Another homeowner says that when he first moved into the area, Heuermann often did woodworking in the driveway but didn’t make any effort to introduce himself. “He never said two words to me,” the neighbor says. “If I saw him at the train station, I didn’t acknowledge him at all. He didn’t acknowledge me.”

The train took Heuermann to and from his professional life working in Manhattan as an architect specializing in building permits. He seemed to take pride in his meticulous planning and exhaustive knowledge of arcane city building codes going back decades. In a video interview conducted by a real estate agent in 2022, he boasted that when permitting difficulties arise on an architectural job, “those calls come to me.” His 26-year-old daughter Victoria was listed as a staff member on the company website.

***

Investigators identified Heuermann as a possible suspect just six weeks after the task force consisting of the Suffolk County Sheriff’s Department, Suffolk County Police, New York State Police and FBI launched. In reviewing evidence collected as far back as 2007 in the disappearances and murders of at least 10 people—mostly women, though there is a male victim as well as a toddler thought to have been killed alongside her mother—authorities used cellphone activity on burner phones used by the suspected killer while he stalked his victims. According to authorities, that data showed that the would-be killer would have been in Massapequa Park and Midtown Manhattan during the time of those calls. Next, the task force used motor vehicle records to track a pickup truck—a Chevy Avalanche—spotted by witnesses in the vicinity of victim Costello on the day before she disappeared. According to court documents obtained by People, that vehicle was traced to Heuermann’s home in Massapequa Park.

Armed with more than 300 subpoenas and search warrants, authorities dug deeper. They secured “abandoned DNA samples” from a pizza crust they allege Heuermann discarded in a Manhattan trash can and from 11 bottles taken from a trash can outside his home. DNA from the pizza crust matched DNA found on a murder victim, authorities say. And DNA and hairs from the bottles matched hairs found on the victims as well. Those hairs were determined to belong to Heuermann’s wife, Asa Ellerup, 59. Because she had been out of the area when each of the women disappeared, detectives believe the hairs were a result of her close proximity to her husband and not because she was involved in the killings. Heuermann’s daughter and a stepson were also out of town when the murders took place.

Investigators also discovered more than 200 Google searches allegedly conducted by Heuermann about the status of the police investigation, and others about the whereabouts of victims’ family members, as well as for rape and torture porn. Records from phone accounts also tied him to sadistic calls made to the families of victims. Among them was a call to Melissa Barthelemy’s sister Amanda days after Melissa went missing in 2009 asking if she was “going to be a whore like her sister,” Lynn Barthelemy, Melissa and Amanda’s mother, told People in 2016. “He would call in the evening and torment Amanda. In his last call to Amanda, he said he had killed Melissa.”

As the task force continued uncovering evidence of Heuermann’s secret double life, a dark portrait of a serial murderer emerged, says Suffolk County D.A. Raymond Tierney. But evidence that he was using burner phones to once again contact women led detectives to arrest Heuermann. “He was using these burner phones and fictitious accounts to contact sex workers,” says Tierney. “We knew we had to take him down, and we thought it would be safer to do it [away from] his home, since he has 92 gun permits. I’d say he was pretty surprised, so we did our job well. I think he lived this double life, and he used the anonymity of phones and computers to shield himself from the rest of society. Unfortunately for him—and fortunately for the rest of us—he wasn’t successful.”

Speaking to reporters outside the courthouse at Heuermann’s arraignment on July 14, his court-appointed lawyer Michael Brown said his client wept as he told him, “I didn’t do this.” Heuermann is being held without bail and is expected to appear back in court in August.

Though the families of the victims are reliving grief all over again as details of the deaths of their loved ones are made public, there is also relief that justice may be served at last. Investigators say a trove of potential clues have been removed from the suspect’s home and storage units. This could lead to additional charges in the upcoming days. “I began to have my reservations about whether this would ever be solved,” says attorney John Ray, who represents the families of possible Long Island Serial Killer victims Jessica Taylor and Shannan Gilbert. “But that still leaves seven other people with their cases unsolved, and we’re hoping that somebody turns the killer in—maybe even the killer himself.”

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