A neighbor of the accused Gilgo Beach serial killer says he and his family have known 59-year-old Rex Heuermann for nearly three decades.

Etienne Devilliers, of Massapequa Park, says he and his wife live next door to Heuermann and that he spoke daily with him.

"He was odd and strange, but never violent," Devilliers says.

Devillers says they moved in 28 years ago and that Heuermann would look over the fence and try to talk to his wife while she would sunbathe in the backyard.

He says his wife felt "creeped out" that Heuermann continuously looked over at her, so he pulled him over to talk.

"We had the talk, and it wasn't a pleasant talk, but he stopped, and he didn't argue with me or anything," Devilliers says. "He just backed off."

LIVE BLOG: Updates on the case as they happen

Since then, Devillers says they became cordial neighbors. He was stunned to learn that Heuermann is accused of murdering three women and is a prime suspect in a fourth murder.

Heuermann is behind bars in a Suffolk County jail.

Suffolk County Sheriff Errol Toulon Jr. tells News 12 he has visited Heuermann three times.

"Twice he has been sleeping, once he was just looking up at the ceiling," Toulon says. "Very quiet, didn't have much to say."

Heuermann is on suicide watch in a cell alone, and Toulon says he has not had any visitors and has two guards watching him.

WATCH: DOCUMENTARY AND BACKGROUND INFORMATION - Gilgo Beach: Unsolved

Toulon says that Heuermann has emphasized that he is not going to be a problem and will be compliant.

The Sheriff's Office Human Trafficking Unit has been showing women in custody a photo of Heuermann.

Toulon says two sex workers previously in custody were contacted by Heuermann.

"They chose not to engage with him, and I do not know the reason they chose not to," Toulon says.