The 31-year-old victim was hit by a southbound Q train at the Prospect Park station just after 2:25 a.m.
Police sources say the victim was reportedly intoxicated when he got into a physical fight with another man.
The two were fighting on the southbound Q-train platform and, as the Q train pulled out of the station, the 31-year-old fell, sources say.
His head was struck by the Q train and he was pronounced dead at the scene.
The other man involved in the fight is believed to be the one who called 911 and he remained on the scene.
The reason for the dispute remains under investigation.
B and Q train service was upended for hours as police investigated.
So far no arrests have been made.
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