Authorities say the victim and the suspect "became engaged in a dispute" before the latter drew a handgun and shot him multiple times.
The gunman was last seen entering the Snyder Avenue and Broad Street SEPTA station and then boarding a southbound train, police said.
He's described as a Black man with twisted braids, wearing a black puffy, hooded coat with red lining in the hood, a black ski mask with a Nike logo on the left side, light grey pants, and black shoes. He has a dark mark, possibly a tattoo, under his left eye.
Anyone with information should call 215-686-8477 or submit an anonymous tip online.
(Note: An earlier version of this story misidentified the victim as 17-year-old Dayemen Taylor. Taylor was killed in a separate shooting on March 4.)
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