Police are looking for a man who they say sexually assaulted a woman on a train in Brooklyn.
Cops say the suspect approached a woman on a southbound 4 train and exposed himself to her.
When she tried to get away from him, cops say the man grabbed her and forced her against a train door.
They say when the doors opened, the victim ran out and told a train conductor.
Cops say the man followed her until she was able to get back onto the train without him.
Anyone who recognizes him, is urged to call police.