Philadelphia police have arrested the man they believe supplied the gun in the shooting that injured two students at Delaware Valley Charter High School.

Authorities say video footage shows 18 year-old Donte Walker exchanging the gun for money with an unidentified male on Friday.

They say the former student was able to bring the gun into the building because he avoided metal detectors as a guest.

They say the gun was then given to suspected shooter Raisheem Rochwell who officials say feared he was going to be targeted in an after-school attack.