Disabled construction worker Bruce Anderson, 59, complained for years about the slightest noise from his upstairs neighbors in their five-story Harlem apartment building.

“I’ve seen him with a mop stick in the hallway, shouting, ‘If you don’t keep the noise down, I’m going to come up there and whip your ass,” one neighbor told The Post.

On Friday afternoon Anderson apparently decided he’d had, and heard, enough.

The angriest man at 26 W. 131st Street grabbed a gun no one knew he had.

He shot the couple upstairs, Hampton “Smithy” Smith, 78, and wife, Yvette Rivera, 62, officials say — and then set his own apartment on fire.

“Come and get me!” he dared arriving cops.

Then he shot himself dead in the head, leaving behind a scene of ash and carnage.

Anderson was a loner who had injured his hip some years back, and did not appear to work, neighbors said.

Smith and Rivera lived above him on the second floor with a pair of cats, and were the sweetest — and quietest — people in the building, still-shocked neighbors told The Post.

For more than a decade, Anderson hollered at the couple simply because they were “walking back and forth in the apartment,” a neighbor and pal of Smith told The Post, asking not to be named.

“Smithy wouldn’t answer,” he said of the times Anderson would bang on the couple’s door.

Mary Hall, 71, has lived in the building for nine years, and now has bullet holes in her wall.

“He would say they were making noise, but they didn’t have nothing up there to make noise with,” Hall said. “Cats can’t make noise, even big ones … I would say, ‘Smithy, what’s going on?’ and he would say, ‘He is crazy. He is complaining about noise.’ ”

About three years ago, “He heard me talking to another tenant and he thought we were talking about him,” Hall remembered. “He knocked on my door and he said, ‘You got issues with me?’

“I said, ‘Baby I don’t even f—king know you. I ain’t talking about you, I don’t know you and that was it.”

“I had no idea he had guns,” said a friend, Ronald Mitchell, 70.

Building superintendent Edgar Palacios agreed.

“That grumpy man, he hardly talked to nobody,” he said, except to complain. “He complained about every little thing.”

Palacios thought of Smith as a second father. “And Miss Yvette, you know, she was a sweet little lady,” he said.

He can’t imagine they made much noise at all, the super added.

“Walking? Something like that. but they don’t have any kids in here . . . They don’t make any noise.”

Why didn’t Anderson just move away, he wondered.

“You put up with that for 10 years. You don’t look for another apartment?”

Additional reporting by Laura Italiano and Sara Dorn