An argument aboard a Queens subway train turned deadly Wednesday when a madman pulled out a sharp object and fatally stabbed a fellow passenger during the evening rush, police and sources said.
The bloodshed erupted around 5:20 p.m. aboard a packed southbound J Train as it approached Woodhaven Boulevard station, according to authorities.
During the heated exchange, the suspect plunged the sharp object into the 59-year-old victim before barging off the train at the Woodhaven stop, law enforcement sources said…