A play date turned deadly for a 9-year-old girl on Long Island Sunday when she was attacked by a vicious pit bull whose owner even called him a “Beast!’’ on Facebook.

The tragic child was playing with two little pals in the back yard of 236 Holland Ave. in Elmont around 10:30 a.m. when a neighbor’s 2-year-old male pit bull named Kane charged at her, refusing to let go despite the efforts of several neighbors to free her.

“He was holding her somewhere on the side — I don’t know if it was the ears or the neck — and he was throwing her around like a rag doll,” said a next-door neighbor.

“The two [other] little girls ran down the street, screaming, ‘Help! Help! Help!’ I tried to take my broom and push the dog off through the fence. And the doctor up the block was trying to help, too. He threw a garbage can at the dog, but he wouldn’t let her go.’’

When cops arrived, the dog tried to attack them, and one of the responding officers fired three shots and killed him, authorities said.

Meanwhile, the mortally injured child, whose name was withheld by authorities, was rushed to Franklin Hospital, but died a few hours later, with bites all over her body.

“It was a violent attack,” said Nassau County Detective Michael Bitsko at a press conference at the scene Sunday afternoon. “We don’t know why the pit bull attacked her.”

The pit bull’s owner, 29-year-old Carlyle Arnold, who lives on the second floor of the home, was arrested at the scene on an unrelated charge, according to police.

In April, Arnold uploaded a Facebook photo of himself and his muscular dog engaged in a playful tug of war. Kane was wearing a heavy metal dog collar and chains. Arnold captioned the photo, “Beast!”

Arnold’s father, Carlyle Sr., said he was stunned that Kane would attack a child.

“I don’t know what to say, what to do,’’ the dad said. “This is crazy. I’m getting off of work, and now I’m in a horror scene.”

Arnold’s uncle, Anthony Jett — who lives in the house where the attack occurred but wasn’t home at the time — said Kane was a tough dog but usually interacted well with people.

“He was a good dog — that’s what I don’t understand,” Jett said. “He was a beast because he was a pit, but he was very gentle.”

He said he believes that something must have triggered Kane.

“Dogs can flip sometimes,” he said. “They don’t respect kids like they respect adults.”

Neighbor Vito Rendace added that Kane was an “OK’’ dog.

“I mean, if somebody came too close to the house, he would react,” he said. “He would start barking. But that was the extent of it. I never thought he would maul anybody.”