"It looked like a horror movie in there," said an NYPD detective after seeing the blood-drenched bed in the couple's sixth-floor studio on East 89th St., where cops say music producer Danny Harrison was stabbed twice in the chest with a long butcher knife by his live-in lover just before 1 p.m.
A neighbor, who did not want her name printed, said that when Harrison was wheeled out on a stretcher into an ambulance, "he was covered in blood from head to toe, with a huge gash across his chest."
He was pronounced dead at 1:45 p.m. at New York Hospital.
Harrison's girlfriend — 37-year-old Kathleen Connors — was brought out in handcuffs by cops, wearing no shoes, her jeans and feet spattered with blood.
The tall, gaunt woman sobbed as she was placed into a squad car.
Connors told cops that she and Harrison had argued when he complained the apartment was a mess and that he struck her in the head with his hand, according to sources.
She said she grabbed a knife to defend herself and then stabbed Harrison.
"There was shouting, bodies slamming the walls. I could hear bodies and furniture and things flying," said a downstairs neighbor.
"There was no mistaking it, it was definitely an all-out, abusive fight. It sounded like they were both hurting each other. This lasted between 15 and 20 minutes."
Charges against Connors — who sources say has a history of prostitution arrests — were pending.
Sources said Harrison had met Connors through a mutual friend and they started dating several months ago.
A man who lives on the same floor as the couple said he heard Connors screaming at Harrison last month, using "real nasty, real bad language."
Ten minutes after that outburst, the neighbor said, he saw them getting on the elevator together "and they were simpatico."
Harrison's death stunned his friends and acquaintances. "I'm in shock," said a longtime business associate, who asked not to be identified. "It's hard, even now, to believe."
She said Harrison was married three times — twice divorced — and is the father of at least five grown children. His second wife died of cancer two decades ago.
"He was Mr. Mom. He brought those kids up by himself," she said.
Harrison previously had been a psychologist who gave up his career and went into the music business.
Most recently, he worked at a Manhattan music-production company and handled events at such venues as the Manhattan Center, the Tribeca Film Festival, MTV and VH1.
Before that, he had been a tour manager for Simon, notably on the singer's "Graceland" tour, and also had worked with the Eagles, Joel, Dan Fogelberg and Boz Scaggs.
A close friend of Simon told The Post, "He offers his deepest condolences to his family."
Another friend of Harrison, who requested anonymity, called him "a hell of a nice guy" who enjoyed writing and bicycling. "He rode his bike everywhere," said the friend.
Harrison's sixth-floor neighbor also said that the victim was "a decent guy," but added, "It looked like he may have had a drinking problem."
"He had that look," said the neighbor, who had seen Harrison toting liquor bottles back to his apartment, and who on several occasions had to wake him up to tell him that he had left his keys in his apartment door.