Police began a manhunt for the gunman who shot 17-year-old Kareem York in the leg outside Chester High School, prompting a lockdown of the high school and a nearby elementary school.

Police told the Philadelphia Inquirer the suspect was not a student and was still at large at midday. Classes were dismissed for the day.

The motive for the shooting was not clear. York’s family described him as a good student and basketball player who was not involved in any gang activity.