By Molly Daly

PHILADELPHIA (CBS) — A 17-year-old Philadelphia schoolboy is in custody today. Police say he brought a handgun to school.

The incident occurred just before 9am this morning at the De La Salle in Towne School, in center city, as the student was being screened with a metal detector.

Philadelphia police were called when the gun was detected, and the teenager was taken into custody for questioning.

The school is an archdiocesan day treatment center for troubled teens who have been through the court system.