Former Mayor Rudy Giuliani bizarrely showed up at the Long Island residence of the suspected Gilgo Beach serial killer Saturday — driving up and asking an officer how close he could get to the home. 

Giuliani stayed inside his car, chatting with police outside the Massapequa Park home of Rex Heuermann, as it was being searched by law enforcement.

He then drove away.

He didn’t respond to a call seeking comment.

The investigators who swarmed the home Saturday were wearing hazmat suits, gloves and head coverings.

“We’re just going through his house looking to see if there’s any evidence,” a police source told The Post of the search of the alleged killer’s home.

“If he has any trophies.”

At one point, officers pulled a wooden and glass display case out of the home that had a blond, child-size doll wearing a red dress inside.

As law enforcement combed through Heuermann’s home, neighbors nearby held a block party, where one woman recalled seeing the suspect walking his dog.

“He said hello to my son,” the woman, a mom of three who gave her name as Megan, recalled.

“I’ve never spoken to them. … I was surprised. You don’t expect a suspected serial killer to be living around the corner.”

Erica Harmon, who grew up six houses down the street, said her mom once visited the house as a North Babylon census taker.

Detectives spoke to the older woman, who now lives in Florida, about the experience.

“My mother worked for the census back in 2010 and she was allowed in the house and she noticed it was a disgusting mess,” Harmon said.

“It was like a pigsty.”

There was a disconnected burner stove in the middle of the living room, Harmon recalled, adding her mom told her she had “a creepy feeling” being there.

She said her mom asked him questions about how many rooms the home had and if she could look.

“He didn’t try anything,” Harmon said.

“He was respectful. I guess she wasn’t his type.”

She said Heuermann’s daughter does not live there but visits and that she’d recently seen her standing outside on the porch.

“My heart goes out to her,” Harmon said. 

“It’s a sad, scary thing.”

In Midtown, Manhattan, where Heuermann worked as an architect in a Fifth Avenue office building, a sandwich shop owner said the suspect was “a regular.”

“He’s my regular customer,” said Hassan Alborat, owner of Gardenia Deli on Eighth Avenue between 30th Street and 31st Street.

A suspected serial killer has been arrested over the notorious Gilgo Beach murders in Long Island, The Post can confirm.

Rex Heuermann, 59, a married dad of two and architect at a New York City firm, has a home on 1st Avenue in Massapequa Park, sources told The Post.

His arrest is tied to the “Gilgo Four,” four women — Melissa Barthelemy, 24, Megan Waterman, 22, Amber Lynn Costello, 27, and Maureen Brainard-Barnes, 25 — found wrapped in burlap within days of each other in 2010. 

The body of Barthelemy was first found along Ocean Parkway on Dec. 11, 2010, sparking fears of a serial killer in the area.

By spring 2011, the number of bodies had climbed to 10, including eight women as well as an unidentified man and toddler.

Heuermann’s arrest comes after Suffolk County’s new police commissioner created a special Gilgo Beach Homicide Investigation Task Force in February 2022.

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“It’s disgusting. He never talk a lot, just buy a sandwich, sometimes soda or water.”

Alborat said he saw the alleged killer once every two weeks or so and that he never thought badly about him until he heard about the arrest.

“He’s a sick mother——,” he said.

“Thank God they got him.”

With additional reporting by Jon Levine.