Rex Heuermann, the suspected Gilgo Beach serial killer accused of dumping his victims in the brush alongside Ocean Parkway east of New York City, has been charged with a fourth murder.

Heuermann already faces six charges total in the deaths of Melissa Barthelemy, 24, Megan Waterman, 22, and Amber Costello, 27. Suffolk County District Attorney Ray Tierney called him the prime suspect in the death of the fourth victim, Maureen Brainard-Barnes, 25, when he announced the first set of charges last year.

A superseding indictment handed down Tuesday charges Heuermann with the second-degree murder of Brainard-Barnes.

Heuermann entered the courtroom Tuesday morning in a dark suit. His attorney, Michael Brown, entered a not guilty plea and reserved the right to make a bail application. Heuermann was remanded without bail on the new indictment and is due back in court on Feb. 16.

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Speaking to reporters afterward, Brown disputed the DNA evidence in the case, saying this is the first mention of nuclear DNA and that he believes the mitochondrial DNA does not show a match with enough specificity. He said statistically there could be 600 matches in Nassau and Suffolk counties.

He suggested that Costello's pimp, who had described Heuermann as an ogre and gave the description of the Chevy Avalanche that investigators have linked to Heuermann, is a drug user and not credible.

Asa Ellerup, Heuermann's estranged wife, attended his court appearance Tuesday. Her attorney, Bob Macedonio, said afterward that it was a "horrible day."

The indictment "again makes clear that Asa Ellerup and her children were not involved, even in the jurisdiction, when these murders took place," he told reporters.

Heuermann's arrest on July 13, 2023, "was a surprise to Asa Ellerup and her children," he added. "This life that existed, or may have existed, they were completely unaware of."

Heuermann led a quiet life in a New York suburb for decades with a wife and two kids, one of whom grew up to work with him at his Manhattan architectural firm. 

Neighbors knew him as a local businessman who walked to the train in a suit and carried a briefcase, sometimes stopping at the local bars after work and doing a shoddy job keeping up the maintenance on his house, which has cedar shake shingles with peeling paint in a neighborhood where everyone else has since upgraded to vinyl siding.

Then, in July, prosecutors in neighboring Suffolk County identified him as the prime suspect in a cold case serial killer investigation that has mystified area residents and true crime followers since 2010 – the Gilgo Beach murders.

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Heuermann stands 6-feet, 4-inches tall and has been described by former Suffolk County Police Commissioner Rodney Harrison as both a "demon" and an "ogre." Despite his quiet demeanor, police allege he brutally killed the women and hid their bodies in camouflage burlap material.

Tierney announced charges against Heuermann Tuesday for the fourth of the "Gilgo Four" victims – a group of women found dumped close to one another off Ocean Parkway about 45 miles east of New York City.

He had been charged with the other three in 2023, more than a decade after the first bodies were found.

The case unfolded after police received a haunting 911 call from Shannan Gilbert in 2010 and began searching for her near Oak Beach, a few miles to the east.

Crews looked through the dense brush north of Ocean Parkway for months, uncovering the Gilgo Four and a half-dozen other bodies before they finally found Gilbert's remains.

Years later, police said that they believed Gilbert's death was not a homicide. Officially, it has been deemed undetermined, but Suffolk County Police Lt. Kevin Beyrer told reporters in May 2022 that other evidence suggested she had died by accident.

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Brainard-Barnes was last seen on July 9, 2007; Barthelemy on July 10, 2009, Waterman on Jun 6, 2010, and Costello on Sept. 2, 2010.

A police officer named John Malia was running a K-9 training exercise near Gilgo Beach on Dec. 11, 2010, when his dog Blue led him to Barthelemy's remains. Two days later, Suffolk County police recovered Brainard-Barnes, Waterman and Costello, and autopsies identified the cause of death for all four as "homicidal violence."

Each had been dumped between 22 and 33 feet from the edge of the road, according to investigators. Ocean Parkway runs east and west along the Atlantic Ocean outside New York City. Despite the proximity, there are few homes and businesses along the route.

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According to court documents, all four victims shared several things in common – they were sex workers, they were missing clothing and "personal possessions," and all had been in contact with someone using a "burner" phone.

They were all positioned the same way, had been bound in similar fashion – and three were wrapped in the camo burlap material used to make duck blinds, according to authorities. 

Additionally, all four were "petite." Barthelemy, Costello and Brainard-Barnes were all less than 5-feet tall, according to Suffolk County police. Waterman's height is not listed with the others on the department's Gilgo news website.

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In Brainard-Barnes' and Barthelemy's cases, the victims' phones had been used to repeatedly taunt their families after the murders, prosecutors allege.

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The investigation, however, languished for years – before Tierney and Harrison announced a new task force dedicated to crack the cold case.

Six weeks later, the Gilgo Beach investigators found their first major break, Tierney said. A witness in Costello's disappearance had identified a "first-generation" Chevrolet Avalanche pickup truck as the suspect vehicle – and authorities discovered one fitting the description had been registered to Heuermann.

Additionally, advances in mitochondrial DNA testing technology also allowed investigators to link existing hair samples to the suspect's household.

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Three hundred subpoenas and search warrants later, investigators were looking at him as their prime suspect.

Hair samples taken from tape used to bind the victims matched his wife's DNA, according to prosecutors, although she is not a suspect. 

"During the commission of those murders, the defendant's wife and children were out of New York state, and he was alone in the tri-state area," Tierney said during Friday's news briefing. Investigators believe the hair was transferred to the victims from the tape, burlap or other items Heuermann allegedly used in the crimes.

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Further DNA testing found Heuermann's own hair in the camouflage burlap found on Waterman, according to court filings. It also matched DNA found in a pizza box police allegedly watched him toss in a New York City trash can in January.

At the same time, investigators found consistent links between the phone records of Heuermann, his alleged "burner" phones and the victims.

"For each of the murders, he got an individual burner phone, and he used that to communicate with the victims," Tierney said. "Then, shortly after the death of the victims, he then would get rid of the burner phone."

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He had a new "burner" phone with him in Manhattan when police arrested him Thursday, authorities said – which shared a connection to an email account he'd used in the past.

They even found about 200 Google search records showing he was closely following news about the Gilgo investigation, as well as podcasts and documentaries. 

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He was watching the investigators, Tierney said, so the task force kept its work under a tight lid.

"He was searching, compulsively searching pictures of the victims, but not only pictures of the victims, pictures of their relatives, their sisters, their children, and he was trying to locate those individuals," Tierney said.

When Heuermann was not looking for updates on the Gilgo case, he was searching for gruesome and illicit pornography, prosecutors alleged, and he allegedly continued to "patronize sex workers" until shortly before his arrest," Tierney said previously.

Heuermann was born and raised in Massapequa Park, New York. He bought his childhood home from his mother in the 1990s and moved his own family there. Neighbors described him as quiet and unassuming, but some said they got creepy vibes from the unkempt home, which has aging siding, twisted flashing along the roof and two-by-four lumber holding up the front awning.

Stay with Fox News Digital all day for updates and analysis on today's indictment.