New York- A Brooklyn hospital cop who ran a gay-sex Web site was beaten to death and then mutilated inside his own apartment, law enforcement sources said yesterday.

Police were investigating last night whether Nubian Knight’s Internet sex business led to his brutal killing, sources said. Knight, 37, was pounded over the head until he died inside his Bedford-Stuyvesant home. His throat was cut after his heart stopped, sources said.

Knight, who has worked at Kings County Hospital for the past 13 years, had been missing for several days.

“He was last seen picking up his paycheck Thursday at 3:30 in the afternoon,” a source said. “He never reported to work Friday for the midnight shift.”

Cops discovered his body just after 11:30 a.m. yesterday inside his apartment at the corner of Jefferson and Throop Aves., police said.

Knight’s sister Danielle Singleton said his given name was Tyrone Alston, but he had changed it years ago. He apparently took his new name from the comic book hero Nubian Knight – an ordinary black man living in South Africa who one day is blessed with super powers.

Singleton, who visited her brother’s apartment last night, did not mention his sex business. She suggested he may have been killed over money.

“He was a happy-go-lucky, jovial individual,” she said. “He wasn’t the type to have enemies. Everyone wanted to be Tyrone’s friend. I still can’t believe it.”

Singleton said her brother had an 8-year-old daughter who didn’t live with him.

NYPD detectives questioned neighbors in the three-story building throughout the day. Several of them told investigators that Knight “had men coming in and out of his house all the time,” a law enforcement source said.

No arrests had been made last night.

The city’s 850 hospital police officers, employees of the city Health and Hospitals Corp., are not members of the NYPD, and do not carry guns. An HHC spokeswoman said Knight was hired in 1990.

A Web page apparently set up by Knight describes him as a single male cop from Brooklyn. It lists his interests as “submission, wrestling … Brooklyn and dominance.” His favorite quote, according to the site, was: “Tell your story walking.”