On Monday, Police released surveillance video of the October 24th incident.
According to investigators, it happened around 12:30 p.m. that day as the victim was riding the Route K bus.
Police say that's when the suspect sat next to the victim, a 19-year-old woman who is deaf, and indecently assaulted her.
The teen got off the bus at Greene Street and Chelten Avenue. Police say the suspect followed her to the 5500 block of Greene Street where he pulled her into an alley.
The victim was able to escape and the suspect fled on foot to the Philadelphia School for the Deaf, where she was headed, in an unknown direction.
The suspect is described as a heavy-set black male wearing a multi-colored striped sweater with a dark shirt underneath. He also wore dark-colored pants and dark-colored shoes.
Anyone with information is asked to contact Philadelphia Police at 215.686.TIPS (8477) or text a tip to PPD TIP or 773847 or through phillypolice.com.