A man suspected of attacking his father with a butcher knife was shot and killed by police officers Sunday after authorities said he refused commands to drop the weapon on the Lower East Side.

Police shut down a stretch of Ludlow Street after the shooting. Surveillance video showed officers quickly entering a building on the block.

At a later news conference, police said officers encountered a man with a butcher knife after responding to a report of an assault. Authorities said the man did not comply with commands to drop the weapon, prompting officers to shoot him.

“Officers entered the building, saw a trail of blood, and responded without hesitation, not knowing what was waiting for them as they went up the stairs. Their actions are a reminder of how officers run towards danger, and not away from it,” said Assistant Chief Melissa Eger.

Eger said the suspect, 54-year-old Wei Chan, was taken to a hospital, where he died.

Police said Chan had cut his father, 75-year-old Cheung Chan. His father was taken to a hospital with a gash on his head and is expected to survive.

The shooting stopped people walking along Ludlow Street, where some witnesses reported hearing the gunshots and seeing the aftermath.

“We just saw all the cars getting by, the guys running, and then the ambulances, the firemen, all of them getting around, and the gurney,” said witness Debora Martyns. “And some guy said he heard four gunshots. So we were like kind of scared.”

Police said Chan had a documented history of mental illness.

The taped-off scene also caught the attention of surrounding businesses.

“I’m not sure this week what the circumstances were but we definitely have a lot of issues with crime in lower east side,” said Kiyo Darner, general manager of a nearby Japanese restaurant.

The shooting remains under investigation.