Exposed: Long Island Serial Killer Suspect's 'Bone-Chilling' Remark About Brutal Slayings

A former client who worked with the suspected Gilgo Beach serial killer detailed a "bone-chilling" conversation she had with the man charged with killing three people, RadarOnline.com has learned, revealing his arrest rocked her to the core.

The woman, who opted to remain anonymous, was shocked to hear Rex Heuermann's name in the news considering she and realtor Jeffrey St. Arromand had worked closely with Heuermann for the past year on a Brooklyn brownstone project.

Last week, the married dad was hit with first-degree and second-degree murder charges in the deaths of Amber Lynn Costello, and Megan Waterman, who were disturbingly bound at the feet or ankles and wrapped in burlap.

Heuermann is also the prime suspect in the death of 25-year-old Maureen Brainard-Barnes, among other corpses found nearby at the Gilgo Beach site. In total, authorities discovered nine women, a man, and a toddler.

The woman client said she spent time with Heuermann by herself.

"She drove him home one time because she actually relocated to Long Island," St. Arromand told the New York Post about his client, noting that the route was pretty "dark and desolate."

Heuermann is a 59-year-old architect who lives in Nassau County and served as the expeditor and architect on the Crown Heights home she purchased in 2002, which she put on the market two decades later.

"I was only with him in my home to review the scope of work. I even gave him a ride to his home in Long Island from Brooklyn," the client shared.

She said there was a particular interaction they had that now gives her shivers down her spine. "At one point on the drive we talked about the Gilgo Beach murders — we even discussed the burlap and why someone would use that."

St. Arromand added that she later called him to chat about the remark made by Heuermann. "And the first thing [Heuermann] said — and she told me this specifically — the first thing he said was, 'I don't know why he would use burlap net.' And she was like, 'I don't know, either.'"

Never miss a story — sign up for the RadarOnline.com newsletter to get your daily dose of dope. Daily. Breaking. Celebrity news. All free.

The client said that she did notice Heuermann's increasingly frustrated demeanor while selling her home.

"Throughout the transaction, he was becoming very difficult to work with, even becoming belligerent at times," she said. "He was constantly arguing with the plumber on the job and questioning his work. Just very odd behavior."

The district attorney said law enforcement officers used DNA samples and cellphone data to track him down.

Heuermann's lawyer, Michael Brown, claimed the evidence was circumstantial. He also said his client denied wrongdoing by claiming, "I didn't do this."