UPDATED: 8/24/2011 5:38 p.m.

CHICAGO (CBS) — A 16-year-old has been charged in the rape of a 68-year-old woman at a Gary train station earlier this month.

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Aarion Mosley of Gary has been charged as an adult with rape and robbery in the Aug. 13 attack of the woman as she sat in a passenger shelter at the Miller South Shore station during a late night rainstorm.

Police said Mosley rode up on a bike, sat down next to the victim, pulled out a gun and assaulted her. The attack was captured on Northern Indiana Commuter Transportation District parking lot security cameras.

Officers picked up Mosley for questioning Monday at Lew Wallace High School where he was starting his sophomore year.

The woman was sitting on a bench at the station, at U.S. Route 12 and Lake Street, eating a sandwich and seeking shelter from a rainstorm. The assailant approached the woman, chatted with her, then pulled out a gun as he forced her onto the floor, police said.

Police said they were able to connect Mosley with the attacks after arresting him the next day for breaking into a car in the parking lot of the same train station. He was caught on surveillance tape riding away from the scene of the alleged rape, police said.

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Gary school officials said transit police came to Lew Wallace High School on Monday to question the teen. The school immediately called his parents.

Police said that, during questioning, Mosley admitted his involvement in the rape.

Those who know Mosley, who is a sophomore at Lew Wallace High in Gary, said they are stunned. They said he was not only a cadet in Jr. ROTC, but trying out for the football team.

School officials said Mosley was considered a very quiet child and he never had a disciplinary problem at the school.

Police said that surveillance video played a big part in Mosley’s arrest. Miller businesses gave police a series of videos from their security cameras.

In one of those videos, a transit officer recognized Mosley as a person he arrested at the Miller Station for breaking into a car on the day after the rape.

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Police also said they’ve recovered a BB gun, bicycle and clothing worn by the suspect at the time of the attack. DNA evidence is also being analyzed.