Originally Published: 18 JUL 23 03:59 ET

Updated: 18 JUL 23 16:48 ET

By Elizabeth Wolfe, John Miller and Lauren Mascarenhas, CNN

(CNN) — Family members of the Gilgo Beach serial killings suspect were shocked, disgusted and embarrassed when they learned about the crimes he is accused of committing, police say.

“It’s a very good thing that we got this animal off the streets,” Suffolk County Police Commissioner Rodney Harrison said on CNN’s “Erin Burnett OutFront” Monday night.

Rex Heuermann, an architect and father of two, was under 24-hour surveillance before he was arrested Thursday and charged with murder in three of the “Gilgo Four” slayings, according to the police commissioner.

He pleaded not guilty to the killings of Melissa Barthelemy, Megan Waterman and Amber Costello and remains the prime suspect in the killing of a fourth victim, Maureen Brainard-Barnes, according to court documents.

Though he has yet to be charged in the death of Brainard-Barnes, Suffolk County District Attorney Ray Tierney told CNN he is “confident” prosecutors will be able to bring a charge in that case.

Heuermann obsessively followed the case of the Gilgo Four, a group of four women whose remains were uncovered more than a decade ago near Long Island’s Gilgo Beach, authorities say. His internet history revealed at least 200 searches for information about the investigation, as well as compulsive searches for photos of the victims and their families, prosecutors say.

Heuermann’s family was shocked when investigators told them about the allegations against him, Harrison said. “They were disgusted. They were embarrassed,” the commissioner said. “So, if you ask me, I don’t believe they knew about this double life that Heuermann was living.”

As prosecutors brought the case to a grand jury last week, authorities were concerned that Heuermann could find out about the proceedings and try to evade arrest, possibly by leaving the country, Harrison said.

When Heuermann was being processed at the jail following his arrest, he had just one question, a source said: “Is it in the news?”

Despite an arrest in the case, investigators say their work is far from over.

Authorities are “actively investigating” whether Heuermann may have had more alleged victims, Deputy Police Commissioner Anthony Carter said Monday on “CNN Tonight.”

It was “always a concern” that Heuermann may have set his sights on a future victim, Carter added.

A search of Heuermann’s Massapequa Park, Long Island, home revealed a hoard of between 200 and 300 guns that had been stashed in a walled-off vault which was locked behind a metal door, a source with knowledge of the case told CNN. The stash included pistols, revolvers and semi-automatic rifles and was far more extensive than the 92 firearms authorities knew Heuermann had registered in the state, according to the source.

As investigators scour Heuermann’s home, office and a storage unit he kept, they are looking for any “out of place” items, a source familiar with the case told CNN.

Though the searches are primarily focused on gathering forensics, authorities are also keeping an eye out for items that could be hidden or surreptitiously stored souvenirs from the killings, the other source with knowledge of the case said.

Heuermann’s next-door neighbor, Etienne Devilliers, told Fox News that Heuermann was odd, but never came across as violent.

“Nobody in the neighborhood ever talked to the guy,” Devilliers said. “The house was a mess, but he stayed to himself, pretty much.”

Devilliers said he once had to ask Heuermann to stop trying to speak to his wife over the fence when she was in the backyard sunbathing. “It wasn’t a pleasant conversation,” he said. “We spoke pretty harshly, but he didn’t get aggressive or anything, and after that, he never did it again.”

The neighborhood, now filled with investigators and reporters, has become a “madhouse,” said Devilliers.

“We’re in shock. We really are,” he said. “I’m a retired city fireman, and there’s a lot of cops and firemen in the neighborhood, so we feel very, very safe.”

Source: Police looking into possibility of more killings

As authorities painstakingly search for evidence, they are operating under the assumption that the suspect could have continued his alleged killing spree after the Gilgo Four were discovered in 2010, which may lead to a prolonged investigation, a source familiar with the case said.

Investigators may need to review pieces of evidence with victims’ family members and friends to determine if they are souvenirs from the killings, another source said. “This investigation is still in its infancy,” Carter, the deputy police commissioner, said Monday. “We have a long way to go. We have a lot of evidence to process, a lot more witnesses to interview and tips are still coming in.”

Heuermann was first identified as a potential suspect in early 2022, shortly after a multi-agency task force was convened to examine the cold cases involving nearly a dozen sets of human remains found along Long Island’s South Shore between 2010 and 2011, including the Gilgo Four.

Investigators were able to connect Heuermann to at least three of the killings using cell phone data, credit card bills and a sample of DNA taken from a pizza crust the suspect discarded in a Manhattan trash can, according to prosecutors.

Though prosecutors have said Heuermann is the prime suspect in the fourth killing of Brainard-Barnes, he has yet to be charged in the case. Police commissioner Harrison said Monday that a charge in the case may “take a little time” because a hair follicle they collected as evidence was damaged and needed to undergo DNA testing.

Meantime, law enforcement is sifting through a “flood” of tips and evidence that have come in following Heuermann’s arrest, Tierney, the district attorney, said Monday.

“We have a description of the last individual who saw the final victim, Amber Costello, alive that matches that of this defendant, who has a rather unique physical appearance,” Tierney added. “We have phone evidence, and we also have that DNA evidence.”

Heuermann’s DNA was found on one of the bodies, and his wife’s DNA was found on two bodies, Tierney said.

“With regard to that DNA and those hairs, it’s either transfer – in other words, one person comes into contact with a second person who then comes into contact with a third person – or, they were at a location where, you know, the family member occupied, whether it’s a car or a house,” Tierney said.

Property in South Carolina gets visit from authorities

The search for clues has extended to South Carolina, where a neighbor of the suspect’s brother was approached by the FBI on Tuesday as he talked with a CNN crew.

He told CNN’s Dianne Gallagher a green Chevrolet Avalanche was hauled away last week from the property where Heuermann’s brother lives.

It was a Chevy Avalanche that was towed from the lot, which is owned by Rex Heuermann, sources told CNN.

According to two law enforcement sources with knowledge of the case, years ago a witness told investigators they saw the killer driving a green pickup.

In addition to New York and South Carolina, Rex Heuermann owns property in Las Vegas. Police there told CNN they are reviewing unsolved cases for any possible connections to him.

Victims found buried in similar way, police say

The remains of the Gilgo Four were found within three days of each other along the same quarter-mile stretch of Ocean Parkway – each wrapped in camouflaged burlap, according to authorities.

“They were buried in a similar fashion, in a similar location, in a similar way. All the women were petite. They all did the same thing for a living. They all advertised the same way. Immediately there were similarities with regard to the crime scenes,” Tierney said last week.

Three of the women – Costello, Waterman and Brainard-Barnes – worked as escorts and Barthelemy was a sex worker, according to police. All four women advertised their work on Craigslist.

Barthelemy was last seen at her apartment on July 12, 2009, when she told a friend she was going to see a man, according to a Suffolk County website about the killings.

Brainard-Barnes was last seen in early June 2007 in New York City and Costello was last seen leaving her North Babylon home in early September 2010, according to police. Waterman was last seen in early June 2010 at a Holiday Inn Express in Hauppauge.

“These victims were mothers, daughters and people in the community,” Carter said Sunday. “Nobody deserves what happened to them. … To bring their families and bring the victims themselves justice – it is long overdue.”