Police say she saw something, so she said something
MBTA Transit Police report they are looking for this guy, who, they say, exposed himself to a woman on a Red Line train:
On Friday, July 20, 2012, at 11:00 AM, the male depicted below, exposed his genitals to a female victim, then masturbated on a northbound, Red Line train between Park Street and MGH stations. The victim exited the train at Harvard Station. The suspect remained on the train.