CHICAGO (CBS) — A 12-year-old girl was sexually assaulted last year after leaving a convenience store in the East Garfield Park neighborhood on the West Side.

Sometime between Sept. 24 and Oct. 7, the girl was leaving the store about 4 p.m. when a masked male grabbed her from behind and pulled her into an alley in the 700 block of North Lawndale Avenue, according to an alert from Chicago Police. He then sexually assaulted her for roughly 20 minutes before running off toward Ridgeway Avenue.

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The suspect is described as a black male, standing between 5-foot-8 and 6-feet, police said. He was seen wearing a face mask, black gloves, black pants and black Jordan sneakers.

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Anyone with information about the sexual assault should all CPD’s Special Investigations Unit at (312) 492-3810.

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