The homeless man charged in a deadly Chinatown rampage is a drugged-out weirdo who’s been living in an abandoned Bronx building since his family kicked him out of their apartment next door, neighbors told The Post on Sunday.

An exclusive Post photo shows a room with crumbling walls and mounds of debris inside the house at 691 E. 183rd St., where neighbors said Randy Santos, 24, was staying before his arrest early Saturday morning.

A jumbled pile of clothing covered a drop-leaf table next to a filthy gray sofa and a shopping cart, and a white, six-panel door without a knob was propped up against one of the walls.

Santos’ family ordered him out of their apartment in 685 E. 183rd St. about a year ago, neighbors recalled, with one saying, “Something went wrong in his mind.”

“I just saw him on Friday! He didn’t look so good. He was not normal at all, talking to himself, he didn’t look clean. I gave him a plate of food,” said the man, who wouldn’t give his name.

“Someone should’ve helped him, he should’ve been taken to the hospital.”

Eric “E-Money” Tosado, 26, who owns the nearby ET Barber Shop, described Santos as “spaced out” and said he paid him to sweep up “because I knew he needed the help.”

“There was one time he was standing outside for hours — like lost, like he didn’t know what to do,” Tosado said.

“You could tell he was high a lot of the time.”

Tosado also said that Santos has a son who was sent to live in the Dominican Republic about a year ago.

“He didn’t tell me but I think his mom decided to send his son back because his mind wasn’t right,” Tosado said.

There was no answer at the family’s apartment, and Santos’ mom, Fiordaliza Rodriguez, didn’t return a phone message.

Santos’ last known official address was a homeless shelter in Brooklyn, according to the NYPD.