CHICAGO (CBS) — A 14-year-old girl was sexually assaulted Monday while walking to her high school in Burbank, Illinois, police said.

The girl was on her way to St. Laurence High School, walking north on Central Avenue from 79th Street, when police say a man walked up to her from behind, threatened her with a gun and forced her into a nearby alley on the 7800 block of Central Avenue.

She was then assaulted in the alley behind a garage.

The person is described as a black male, about 17 to 20 years old, between 5 feet 9 inches and 5 feet 11 inches tall and about 150 to 170 pounds. He was wearing a reddish-orange pull over sweatshirt and black pants and caring a black backpack.

(Credit: Burbank Police Department)

Police are asking for help identifying the man they believe to be responsible.

(Credit: Burbank Police Department)

He was last seen walking east on 79th Street from Central Avenue after the incident, police said.

(Credit: Burbank Police Department)

The victim is cooperating, and the investigation is ongoing, police said.

The incident took place blocks away from a school campus, near a busy intersection.

A home security camera in the alley captured the images of the suspect. The owner of the security camera said you can hear the suspect threatening the girl in the video.

Anyone with information is asked to call the Burbank Police Department at (708) 924-7300.