A top investigator on the Gilgo Beach serial killings task force has described the suspect, Rex Heuermann, as a "demon" and said it's possible there may be more victims out there.

Heuermann, 59, was taken into custody in New York City Thursday and charged with murder in connection to the killings of three of the four women who became known as the "Gilgo Four," CNN previously reported.

The unsolved killings terrorized residents and confounded authorities on Long Island's South Shore after a woman's 2010 disappearance led investigators to find at least 10 sets of human remains and launched the hunt for a possible serial killer.

The New York architect's arrest came more than a year after the task force explored his possible connection to the cold case named for the beach where the remains were discovered.

Heuermann has pleaded not guilty and was remanded in custody Friday. He is the "prime suspect" in a fourth murder, prosecutors said.

In a rare insight into the investigation, Suffolk County Deputy Police Commissioner Anthony Carter told CNN the multi-jurisdictional task force is still working full time.

When asked if there may be more victims, Carter said, "I think in the coming days, as we continue to gather evidence, anything is possible."

"There are still things that we have to do. There are still human remains that have to be investigated further in Gilgo," he said. "I can't begin to imagine the pain that these families have had to endure over the last decade and to know that this demon was capable of doing such an evil act to these families, it is just, you know, beyond comprehension."

"It's really hard to get into the mind of somebody that's capable of committing the crimes that he committed," Carter continued, adding that "the acts that (the suspect) committed were the worst I've ever seen."

Investigators got sample of suspect's DNA from pizza in the trash

The multi-jurisdictional task force was formed in early 2022, three days after Carter took on the role of deputy commissioner. It includes investigators from Suffolk County Police, New York State Police, the Sheriff's Department, the District Attorney's Office, the FBI and others.

"The detectives in this case... they never quit," Carter said. "They've been working this case for over a decade and they never quit."

The case was broken open in part thanks to cell phone data, credit card bills and DNA testing, authorities have said. In January 2023, investigators got a sample of Heuermann's DNA from leftover crust in a pizza box he threw in the trash.

"There was a lot of persistence and a lot of detailed planning that went into all of that," Carter said of the task force's attempts to get a viable testing sample of their suspect's DNA. "Between our undercovers and really the full power of the task force, we were able to finally get that abandonment sample."

Carter said he was out exercising on a run Thursday when the call came through from Suffolk County Police Commissioner Rodney Harrison that the team was moving in to apprehend their suspect in Midtown Manhattan.

"When that arrest finally came, that was the first thing that came into my head was -- we got him," Carter said.

He said the task force feared for public safety and the possibility their suspect may have set his sights on another potential victim.

"There was always a concern and that was the reason why the arrest was made that Thursday evening," Carter said, noting it was a "very dangerous and delicate balance that we had to navigate through."

Carter said investigators are still looking into the suspect's whereabouts and conduct up from when the women's remains were discovered in December 2010 up until Thursday.

Investigators are also continuing to comb through details coming in on tip lines and are lining up interviews with witnesses, he said.

Heuermann's wife and two children are cooperating with the investigation, Carter said.

"These victims were mothers, daughters and people in the community that nobody deserves what happened to them. Nobody and, you know, to bring their families and bring the victims themselves justice. It is long overdue but I am very glad that we are where we are today," Carter said.