The man charged with brutally beating four sleeping vagrants to death in Chinatown was an “angry” person who routinely threatened to kill, pointing at other homeless men and saying, “You’re going to die.”

“If he would walk through here right now, he’d point to you and say, ‘You’re going to die,’ he’d point to me and say, ‘You’re going to die,’” a vagrant who knew the alleged killer told The Post.

“If he had a chance to get in your house and you were sleeping, he would have did it to you,” said the man, who declined to give a name but said he is 50 years old. “The killer, he wasn’t sociable. He had a grudge. He was mad at the whole world.”

Randy Santos, 24, is charged with the bloody rampage Sunday that killed four and left a fifth hospitalized in critical condition. Police said Santos used a 3-foot-long metal object to pummel the victims on Bowery Street near Doyers Street.

Santos, who police said has a history of violent crimes, was still clutching the bloodied weapon when police took him into custody.

The vagrant who spoke to The Post said he’s lived on the streets since being released from prison about two months ago. He sleeps in Kimlau Square, where Santos and his alleged victims sometimes slept.

The homeless man said Santos was known in the area, but had no friends.

“They didn’t know them to talk to them. They were not friends. They were not associates,” he said of the victims. “The guys who pushed the bucket (cleaners), they used to tell him to get up in the morning so they could clean. And he’d get angry. He’d get mad at them. He was an angry dude.”

He said he was skeptical that outreach workers who have suddenly materialized — including do-little city employees there Tuesday — would have much impact in the long run.

“They just go on TV and say they’re going to put more people out here,” he said. “(Mayor Bill) de Blasio said he’s going to put more security on the street. But he’s going to do the police a favor. He’s going to pay them overtime.”

“Nothing will change,” he added. “You’re still going to have berserkers out here walking around hungry.”