Toronto police are hunting a man who photographed and sexually assaulted a 15 year-old girl travelling alone on a GO Transit train earlier this week, and then followed her when she disembarked.

A closed-circuit video image shows the alleged attacker to be white, aged 25 to 30, weighing about 180 pounds, unshaven with short brown hair.

He was wearing a baggy black winter jacket, beige pants, a beige baseball hat worn back to front, construction boots and black sunglasses.

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The girl got on the train at Whitby and was travelling west on the Lakeshore East GO Transit line at around 4 p.m. Wednesday when her assailant sat down close by and began taking pictures of her with his cell phone, police said.

As the train approached the Rouge Hill Go Station on Lawrence Avenue East in Scarborough, the suspect then sexually assaulted her.

The girl was able to leave the train at the station but the man got off too, and followed her a short distance before fleeing.

The incident is disturbing, Constable Tony Vella said, and he urged anyone with information to relay it to investigators.

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"The victim's age is obviously one aggravating factor, as well as the fact that it happened in a public area," he said.

"We do have good images of the suspect, and so we're hoping someone can identify who he is.

Maybe from around that time frame there's someone who was on the Go Train."

Anyone with information is asked to contact police at 416−808−7474, or Crime Stoppers anonymously at either 416−222−TIPS (8477), or online at www.222tips.com .