Toronto Police are issuing a heads up about the sex assault of a 15-year-old girl on the GO train.

It happened Wednesday afternoon, as the girl travelled on the Lakeshore East line.

Police say a man sitting close to the girl, looked to be taking pictures of her with his cellphone.

As the train pulled into the Rouge Hill station, the man sexually assaulted the girl.

The girl left the train with the man following her.  Eventually he took off.

He's described as white, in his late 30s with short brown hair & an unshaven face. He was wearing a black, loose-fitting winter jacket, beige baseball hat, turned backwards, beige pants, construction boots & black sunglasses.

If you have any information about this man, call Toronto Police at 416-808-7474 or contact Crime Stoppers.