A Philadelphia woman survived being thrown onto electrified subway tracks on Tuesday, in an attack that was recorded in shocking detail by a security camera.

Police said the video shows a man walk up to a 23-year-old woman and ask for a lighter for his cigarette. Then without warning he grabs her by the throat and punches her several times, steals her mobile phone, throws her to the ground, and then, horrifyingly, drags her onto the tracks.

Police told NBC Philadelphia that they did not release the video immediately because the assailant, who's since been arrested, could only be identified by the jacket he was wearing.

Southeastern Pennsylvania Transit Authority (SEPTA) Police Chief Thomas Nestel told reporters that he made the call to withhold the information in hopes of spotting that jacket out in public again. After stepping up patrols and putting out bulletins to as many officers as possible, they finally spotted the man on Thursday, and he announced on Twitter that officer Nicole Lawson had successfully made an arrest.

Police claim the assailant turned out to be one William Clark, a mentally ill homeless man. The woman who was thrown onto the tracks only sustained minor injuries.

This video is from NBC Philadelphia, aired Thursday, January 17, 2013.

View more videos at: http://nbcphiladelphia.com.