The 16-year-old allegedly fired at least 15 shots inside the school before being shot dead by a passerby, according to Mike Krantz, police chief in the city of Bend.
The perpetrator's possible motive is unknown.
Everyone wants to know why, including us. We may never get the full answer, but we want it, says Mike Krantz.
Three children under the age of twelve and a teacher were shot dead in the attack at 1 p.m. on Thursday. Two more people are being treated in hospital for gunshot wounds.