Video probably NSFW, definitely not safe for kids:
The incident happened around 9:30 a.m. Friday morning, according to Transit officials. A woman recorded the video after she noticed the man was exposed, sitting right next to her.
"When you're in that kind of situation you're more concerned with thinking,‘Am I really seeing what I'm seeing? Is this really happening?’” said Ida Goldkorn.
Philadelphia police have not released the name of the suspect, but they say they know who they're looking for.
It's not always easy to speak up directly in such situations — something that the gross people who touch themselves in public may be counting on. (Some are also mentally ill, so pure evil isn't always the explanation.) So cheers to Ida Goldkorn, who took action.