Man fatally stabbed during argument on J train in Brooklyn: cops

A man was fatally stabbed on a Brooklyn-bound J train Tuesday night when an argument with a couple turned violent, according to police.

The 36-year-old victim and the suspects, a man and a woman, boarded the train in Manhattan around 8 p.m. and as they headed over the Williamsburg Bridge toward Brooklyn, the three began to fight, sources said.

Heated words turned into blows as the train pulled into the first stop in Williamsburg at the Marcy Ave. station, the sources added.

The male attacker, who sources said was wearing a denim jacket, pulled a knife and stabbed the man in the chest, according to the NYPD.

The wounded victim stumbled out of the train when the doors opened and collapsed on the platform, according to sources.

He was taken to Methodist Hospital where he could not be saved, cops said.

The suspects fled the scene and the investigation is ongoing.