The victim is a 19-year-old man.
The incident happened on a crosstown 23rd Street bus in Gramercy Park.
Police say the suspect seen in the video harassed the victim, followed him off the bus and punched him in the head.
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The suspect then jumped back on the bus, which continued westbound.
The 19-year-old suffered pain and bruising but refused medical attention.
Police are asking for the public's help tracking down the man seen in the video.
Call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782). You can also submit tips by visiting the CrimeStoppers website at crimestoppers.nypdonline.org or by messaging on Twitter @NYPDTips.
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