A man has been arrested after allegedly killing two people and injuring a third in an apparently unprovoked stabbing in Manhattan, authorities said.

The first victim, a 36-year-old man, was fatally stabbed in the abdomen at 8:22 a.m. Monday in an unprovoked attack at the construction site where he was working on West 19th Street, the NYPD said.

About two hours later, a 68-year-old man was stabbed multiple times on East 30th Street, police said.

The third victim, a 36-year-old woman, is in critical condition after being stabbed multiple times around 10:55 a.m. at 42nd Street and First Avenue, police said.

The 51-year-old suspect — who lives at the Bellevue Men’s Shelter on East 30th Street — appeared to choose his victims at random, police said.

He was caught near East 46th Street and 1st Avenue, police said.

“He just walked up to them and started attacking them with the knives,” Detective Chief Constable Joe Kenny told a news conference.

The suspect has eight prior arrests, according to law enforcement, and is believed to have serious mental health issues, Mayor Eric Adams said.

“There is a real question as to why he was on the street,” Adams said.

Two bloody kitchen knives were recovered, police said.

“These random attacks left two innocent victims dead and another fighting for her life,” Kenny said. “We have one suspect in custody and are not looking for others at this time.”