Man slashes father before leaping to his death from 46th-floor Upper East Side apartment — (New York Daily News)

A troubled son slashed his deep-pocketed dad and then leaped to his death Wednesday from the 46th floor of a swanky Manhattan building.

Mark Citrin jumped before cops could persuade him to come out of a barricaded bedroom in the family’s Upper East Side condo.

“’No,’” Mark Citrin yelled repeatedly before he went out the window with the bloody knife still in his hand, a police source said. “He was refusing to come out voluntarily.”

An officer who watched the drama unfold from another floor said the doomed 27-year-old tossed a book bag, sneakers, an umbrella and several other items before he jumped.

“He just sat on the windowsill and dived,” another police source said.

Citrin’s father is Niles Citrin, a founding partner at Citrin Cooperman, a Fifth Ave. accounting firm. He was being treated for knife wounds to his face and head at Bellevue Hospital, and his wife was by his side.

“Basically it involved the father being slashed and the son taking his own life,” Chief of Detectives Robert Boyce said outside the multimillion-dollar pad in the Bristol Plaza. “That’s basically it. A father and son, family dispute.”

It was not immediately clear what caused Mark Citrin, a greeter at the famed Gallagher’s Steakhouse in Midtown, to snap and attack his father.

Citrin allegedly barricaded himself into an apartment in the building on E. 65th

He landed on the roof of an adjoining one-story Bank of America building on the Third Ave. side, according to witnesses.

Citrin allegedly barricaded himself into an apartment in the building on E. 65th St. near Third Ave. before his fatal leap.

But his mother told police her son was taking Prozac, a medication used to treat depression and other mental disorders, sources said.

Mark Citrin attacked his dad during an argument about 6:30 a.m. in the building on E. 65th St. near Third Ave., officials said.

While his horrified mother looked on, the unhinged son attacked his father and then fled to his bedroom and barricaded the door.

An NYPD hostage negotiation team arrived a short time later, but before they talk to him, Mark Citrin leaped.

“The officer watching also said the male had a knife in his hand the entire time,” the source said.

Mark Citrin landed with a crash on the roof of an adjoining one-story Bank of America building and died at the scene, officials said.

He studied economics and finance at Emory University and briefly worked at Citigroup and Signature Bank after graduating in 2009, according to his Facebook page.

The son of Nancy and Niles Citrin, pictured, jumped to his death from the family’s high-rise condo after slashing his father in the face.

But of late, Mark Citrin had been working at Gallagher’s, according to his Facebook page.

Workers there said Niles Citrin hooked him up with the job because he didn’t like finance. They said he talked about opening a joint of his own that married fast food with high-end fare.

“He was energetic, he wanted to learn it all,” said a general manager who asked not to be identified. “He was lovely.”

A waiter said Mark Citrin was “very good” at his new job and was too stunned to speak of him in the past tense.

“He is a really nice guy,” he said.

Mark Citrin was the son of a high-achiever. Founded in 1979, Citrin Cooperman ranks 22nd on Accounting Today’s 2015 list of top 100 firms in the nation. And condos at the Bristol Plaza sell on average for about $5 million each, according to the real estate website Streeteasy.com.

With Ginger Adams Otis, Edgar Sandoval, Chelsia Rose Marcius

ttracy@nydailynews.com