An Instagram post helped Monroeville Police track down and arrest the gunman who wounded three people at Macy's store in Monroeville Mall on Saturday evening.

The suspect, 17-year-old Tarod Thornhill, targeted a male victim who was at Macy's. He also wounded two other people when he fired his gun indiscriminately.

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Police reviewed the surveillance video of the mall for a clearer image of Thornhill, who was wearing the same clothes in a picture that was shared on photo-sharing app Instagram by the Pittsburgh Post-Gazette on an arrest affidavit that the publication obtained.

With the positive match, the Monroeville Police Department was able to track and arrest Thornhill, now detained at the Allegheny County Jail. He has been charged as an adult of aggravated assault, attempted homicide and recklessly endangering other people, AP reports.

The shooting victims are confined at the Forbes Hospital, two have critical wounds and one has moderate but non-life-threatening injuries.

Douglas Cole, police chief of Monroeville, said one of the victims was a definite target of the teen gunman and the two others were just bystanders hit by the gunfire from Thornhill.

Following the incident, the mall plans to ban minors on weekend nights if they are not accompanied by adults. Under the Youth Escort policy which would take effect by the end of February, all mall goers who are below 18 must have a parent or guardian at least 21 years old with them.

The policy applies from 6 p.m. on Friday and Saturday. Teens working in the mall would be issued identification cards to allow them access to Monroeville Mall during those window hours, reports WITF.

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