A man who cops said was fatally stabbed near Columbia University on Sunday actually died of natural causes, according to the city Medical Examiner’s Office.

The 63-year-old man was originally thought to have a fatal chest wound. The unidentified male was discovered unconscious on West 112th Street in Manhattan and declared dead just before noon, authorities said.

Meanwhile, about an hour after the man in Upper Manhattan was found dead, a 26-year-old male victim was shot once in the torso by an assailant in Brooklyn on 42nd Street off Farragut Road, according to authorities.

The victim was taken to Kings County Hospital Center, where he was expected to survive, police said.

The suspect fled the scene in a Mercedes Benz, the NYPD said. The investigation is ongoing.

And shortly before 2 p.m., a man in his 20s was shot in the torso in Brooklyn and rushed to the borough’s Methodist Hospital, police said.

The shooting occurred several blocks from Green-Wood Cemetery on 20th Street, police said.

No motive for either shooting was reported by police Sunday.