An unsuspecting Bronx man was killed after going to visit a friend — not knowing death was waiting for him at her front door.

Tyrone Quick, 45, was knifed to death on his near-daily visit to Vanessa Guzman inside an University Avenue apartment in Highbridge, when an unhinged neighbor, Jose Ortiz, 65, allegedly went berserk shortly before 9 p.m. Friday, police and a witness said.

When Guzman sought refuge from an allegedly erratic Ortiz inside another woman’s apartment, the suspect apparently slunk inside behind the 39-year-old, slashing her in the arm — then lay in wait by the door and mortally wounded Quick when he arrived, police said.

The neighbor, Justina Cruz, said she was applying pressure to Guzman’s wound and didn’t know Quick was hurt.

“I had no idea that Tyrone was right in front of my f–king door fighting for his life. I didn’t know or I would have helped him, I would have helped him. I didn’t know,” she said, crying, calling it “like a f–king scary movie, like your worst nightmare.”

She said Ortiz was “just standing there ready to take on anybody that came in, adding, “He said he was gonna kill us. I looked at him and said, ‘You are f–king crazy. You are not going to kill nobody.”

Authorities said the wounded Quick, who lived on Nelson Avenue, then got on the elevator and took it to an upper floor, where he got off the lift and subsequently collapsed.

“Somehow Tyrone had made it to the elevator. I don’t know how but he ended up on the sixth floor. He never goes to the sixth floor. He was just trying to run away,” Cruz said.

Ortiz “waited for cops,” Cruz said, and was taken into custody without incident. He was charged with murder, attempted murder, manslaughter, attempted manslaughter, assault and criminal possession of a weapon. 

Investigators were probing whether “a complaint over noise” fueled the rampage and Quick was caught in the middle.

“That’s preliminary,” a department spokesperson told The Post.

Ortiz had been banging on Guzman’s door, prompting her to call Cruz, Cruz said.

“He [Ortiz] is always banging on the f–king wall and acting like somebody is making noise. He is banging on Vanessa’s door. Vanessa lives by herself. Vanessa has no kids, no pets. Vanessa doesn’t have anything. Vanessa does not even listen to loud music and this man is banging on her wall and causing havoc,” Cruz said.

In the end, Guzman was taken to Lincoln Hospital with non-life-threatening injuries, authorities said.

The Bronx building is home to individuals who were previously homeless as well as low-income residents and individuals with mental health matters.