It happened Saturday at 6:50 p.m. at the Atlantic Avenue station.
Video shows the man punching the 32-year-old victim in the face several times.
The attacker ran off and the victim was hospitalized at Interfaith Hospital for treatment of broken facial bones and cuts. He was listed in stable condition.
Anyone with information in regard to this incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
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