It happened as the train arrived at the Lorimer Street and Broadway station at 2:33 a.m.
The suspect ran off the train at that station and the victim remained on board until the train stopped at the Flushing Avenue station.
Officers responded to a 911 call and found the man with stab wounds to his back and neck.
He was taken to NYC Health and Hospitals/Woodhull, where he was pronounced dead.
There are no arrests and the investigation is ongoing.
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