The incident happened on November 27 shortly after 7:30 p.m.
You can see the suspect as he follows a woman down into the station at 1500 Market Street in Center City's Logan Circle section.
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Police say he touched the woman inappropriately on the buttocks before running away.
You can get a look at his face as he runs back upstairs.
The suspect is described as a black male, 5'7 tall and 130 lbs. He was wearing a coat and a black "scully".
Anyone with information about who he is is asked to call Philadelphia Police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).
All tips will remain confidential.