Suspected Gilgo Beach killer Rex Heuermann engaged in 'disturbing' activity in months before his arrest, Suffolk Police Commissioner Rodney Harrison said 

Suspected Gilgo Beach serial killer Rex A. Heuermann engaged in “disturbing” activity while investigators tailed him in the months leading up to his July arrest in the slayings of three women whose remains were found near Gilgo Beach 13 years ago, Suffolk Police Commissioner Rodney K. Harrison said Wednesday.

“I can’t talk about if he was preparing to kill again …” Harrison said in an interview at Newsday’s Melville headquarters. “He’s somebody that was still engaging in activity that was disturbing, be it his internet searches, be it engaging in other activities that he shouldn’t be engaging in. That’s something I was very, very passionate about, regarding ‘we need to see what his lifestyle is.’ ”

Heuermann, a 59-year-old architect from Massapequa Park, has pleaded not guilty to first- and second-degree murder charges in the killings of Megan Waterman, Melissa Barthelemy and Amber Lynn Costello,  whose remains were found near Gilgo Beach in 2010. Prosecutors have also called Heuermann, who was arrested July 13, the “prime suspect” in the killing of Maureen Brainard-Barnes, whose remains were found near the other three victims. All four of the women were sex workers, officials said.

Investigators linked Heuermann to the killings through DNA obtained from discarded pizza crust and a “used napkin” as well as cell-site data and a green Chevrolet Avalanche he used to own, prosecutors have said. Heuermann’s defense team has said their client, who has no prior criminal record, has professed his innocence.

Heuermann attorney Michael J. Brown did not respond to a message seeking comment Wednesday.

Harrison, however, expressed confidence in the strength of the case and defended public comments he made in which he called Heuermann a “demon that walks among us, a predator that ruined families” during a news conference after the arrest.

“I’m very confident that Mr. Heuermann’s our subject,” Harrison said Wednesday. “Because of my confidence, I’m gonna call him what I wanna call him — somebody that ruined families, somebody who’s a predator, somebody who shattered lives. And not just one, several, and there may be more. I didn’t say that there is, but there may be more. If the family members have a problem with me calling him a demon, then I’ll apologize.”

Harrison, in a wide-ranging interview about the Gilgo Beach serial killer investigation, said he formulated the task force to concentrate on trying to crack the long-unsolved series of killings after getting a briefing from his homicide chief, Det. Lt. Kevin Beyrer, shortly after he became commissioner and learning that only one homicide detective was assigned to the case.

Harrison, a 30-year NYPD veteran who left that agency as chief of department to become Suffolk’s police commissioner in December 2021, said the detective wasn’t working exclusively on Gilgo, but was also juggling other assignments, a situation that “didn’t allow us to put a dragnet over the case.”

“When I found out that there was one investigator assigned to this case, I was like, ‘this case is never gonna be solved like that, especially if this person, this detective, is also catching other cases,’ ” said Harrison, who said he increased the number of investigators to four. “ … We’re going to take these individuals and put them in a place where they’re only looking at Gilgo.”

Heuermann was first identified as a suspect on March 14, 2022, after a state police investigator ran through a law enforcement database the description of a Chevrolet Avalanche that was described by a witness as being seen at Costello’s home on the day before she was last seen alive, prosecutors have said.

The Suffolk County Police Department didn’t have access to that database, Harrison said.

From that time, to his arrest on the night of July 13 outside his midtown Manhattan office, authorities surveilled Heuermann in “a host of different ways,” Harrison said.

It was FBI Special Agent Craig Matteo, according to court papers filed by one of Heuermann’s defense attorneys, who retrieved the pizza crust and napkin purported to have been used by Heuermann from a garbage can. On Wednesday, State Supreme Court Justice Timothy Mazzei ordered Heuermann to provide a cheek swab for further DNA testing in the case.

The FBI almost didn’t join the task force, Harrison said.

“They were reluctant at first,” Harrison said. “They were concerned about, I guess, some past relationships where they weren’t necessarily part of being inside the loop of the case. So I reassured them, ‘that’s not something you have to worry about any further. I need you, I need your expertise.’ ”

Harrison said he “didn’t ask too many questions regarding what happened in the past,” but “They were like, ‘we’re not joining the task force.' ”

Collecting the DNA sample was “instrumental” to arresting Heuermann, Harrison said.

“Once we got Rex in our sights, we had to figure out how to collect his DNA,” Harrison said. “That was something that they really had a major role in, gave us some guidance in sending us to the right labs. … Once we got those matches, I don’t think I need to tell you anything else, that was really a place where we went from reasonable suspicion to probable cause.”

Harrison installed a sergeant and three detectives to work full time on the task force, which in addition to the FBI and state police also includes the sheriff’s office and investigators and prosecutors from the office of “our pit bull district attorney Ray Tierney,” as Harrison put it. The task force meets daily at the Suffolk County Police Academy in Brentwood. Harrison declined to identify by name the Suffolk police department members.

Since Heuermann’s arrest and the subsequent search of his home, storage units and former vehicle, dozens of officials from the medical examiner’s office, the state police and the homicide squad have joined the investigation to process all of the potential evidence that was seized, Harrison said. Authorities have declined to detail the potential evidence, other than 279 firearms that were taken from inside a vault at Heuermann’s home.

Harrison also offered a definitive statement on Shannan Gilbert’s connection to the case.

Efforts to find Gilbert, who was a missing sex worker, led authorities to the remains of 10 other victims — including those of Waterman, Barthelemy, Costello and Brainard-Barnes.

“It’s a horrible accident and as of right now, myself and the investigators assigned to the homicide squad still believe it was just an incident where she ran into the marsh and unfortunately drowned on that horrible day,” Harrison said.

Gilbert’s autopsy concluded her cause of death was “undetermined,” and police have previously said they considered her death to be an accident, though the lawyer representing her estate maintains Gilbert was a homicide victim, citing a second autopsy conducted at the behest of Gilbert’s family that determined her death was “consistent with homicidal strangulation.”

Meanwhile, Harrison said investigators are not only continuing the investigation into the killings in the current indictment, but whether Heuermann could be involved in the other Gilgo killings — or other unsolved slayings in Suffolk County.

“We were able to bring comfort to three families, we’re very close to a fourth one, but we still have more work to do to identify the subject or subjects that were involved with the other bodies that were discovered,” he said.

Should Long Islanders be worried that a serial killer responsible for some or all of the other six killings is still at large?

“I wish I could give you an answer,” Harrison said. “I can’t tell you at this time. Is Rex Heuermann going to be held accountable for the other bodies on Ocean Parkway? Time will tell.”