Suspected Long Island Serial Killer Rex Heuermann Charged with 4th Gilgo Beach Killing

According to prosecutors, burner phones allegedly showed Heuermann searched online for sex workers, audio accounts of rape and "autopsy photos of female"

<p>Suffolk County Sheriff

Suffolk County Sheriff's Office

Rex Heuermann

Long Island Serial killer suspect Rex Heuermann has been charged in connection with a fourth murder, prosecutors confirmed in court documents reviewed by PEOPLE on Tuesday.

The Suffolk County District Attorney’s Office announced on Jan. 16 that the 59-year-old former architect from Massapequa Park has been linked to the killing of Maureen Brainard-Barnes through DNA evidence and has been charged with second-degree murder, according to authorities, ABC New York reports.

Brainard-Barnes was one of  four women found buried in the same marshy, desolate area in Gilgo Beach in Long Island, N.Y., in December 2010, all within about 500 feet of each other. The other victims were identified as Amber Costello, Melissa Barthelemy and Megan Waterman.

All four women had worked as online escorts and were missing between 2007 and 2010. Heuermann, who was previously charged with the murders of Costello, Barthelemy and Waterman in July, has pleaded not guilty to the killings.

Brainard-Barnes was last seen on July 9, 2007, in New York City after checking out from a Super 8 Motel. She was found bound with three leather belts, one of which was used to tie her ankles.

In Tuesday's filing, prosecutors claimed that burner phones were discovered that connected Heuermann to online searches for sex workers as well as porn searches, audio accounts of rape and a search that read: "autopsy photos of female."

Prosecutors further alleged that Heuermann was alone while his now-estranged wife was out of town with their children when Brainard-Barnes was killed in July 2007, ABC New York reports.

This allegedly fit a pattern of him being alone during the other alleged murders which granted him "unfettered time to execute his plans for each victim without any fear that his family would uncover or learn of his involvement in these crimes," prosecutors said in the court documents released Tuesday.

<p>Suffolk County Police Department; Barthelemy family; Suffolk County Police Department (2)</p> Maureen Brainard-Barnes; Melissa Barthelemy; Megan Waterman; Amber Lynn Costello

Suffolk County Police Department; Barthelemy family; Suffolk County Police Department (2)

Maureen Brainard-Barnes; Melissa Barthelemy; Megan Waterman; Amber Lynn Costello

Related: Gilgo Beach Murder Suspect May Have Kept Trophies of Victims — as Police Allege Disturbing Internet Searches

Heuermann was allegedly linked to the previous three cases by other burner phones, which were used to arrange meetings with the victims, as well as by a piece of his hair allegedly found at the bottom of a burlap bag used to wrap Waterman’s body.

He was also traced to a Chevrolet Avalanche registered to him that was allegedly seen at the time of Costello's disappearance. In searches, authorities also found evidence that Heuermann was allegedly obsessed with the case and searched for articles about the task force that was formed to investigate the murders.

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“We saw all this, really sort of concerning searches that he was undergoing,” Suffolk County District Attorney Ray Tierney previously alleged. “In a 14-month period, over 200 times, he’s searching for information about the Gilgo investigation. He’s trying to figure out what we’re up to.”

According to authorities, included in his searches were: “Why could law enforcement not trace the calls made by the Long Island serial killer” and “why hasn’t the Long Island serial killer been caught.”

Related: Suspect in 'Long Island Serial Killer' Case ID'd as Architect Rex Heuermann: Source

Investigators also allegedly found hundreds of internet searches about raping and torturing women, child porn and rape porn as well as searches for his victims and their families.

“He was obsessively looking at the victims, but he’s also looking at the victim’s siblings,” claimed Tierney.

Heuermann also allegedly seemed to be fascinated by serial killers and sleuthed online for “11 currently active serial killers,” and “8 Terrifying Active Serial Killers (We Can’t Find).”

Tierney said Heuermann was "pretty surprised" when he was arrested on July 13 near his office building in Manhattan.

“I think he lived this double life, and he used the anonymity of phones and computers to shield himself from the rest of society," he alleged. "Unfortunately for him — and fortunately for the rest of us — he wasn’t successful.”

Related: Rex Heuermann Allegedly Linked to 2 More Gilgo Beach Victims by Witness Testimony: Lawyer

Bob Macedonio, the attorney for Heuermann’s wife’s Asa Ellerup, previously told PEOPLE that Ellerup was “blindsided” when the arrest happened.

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