Three children, aged 5, 8 and 11, and one teacher were killed when a 16-year-old Bend, Oregon, resident entered Silver Rail Elementary School and started shooting, police said at a news conference Thursday evening.
The shooter, armed with a long gun, forced his way into the school by shooting at locked doors.
A community member who saw the teenager entering the school at about 1 p.m. followed him in before engaging him in gunfire, killing him before responding officers arrived, Bend Police Chief Mike Krantz said.
A 7-year-old child and another teacher were also injured and transferred to a hospital.
Police did not identify the shooter, and said it is not yet clear whether he had any connection to the school or what his motive was. The FBI is assisting in the investigation.
The tragedy marks the 36th shooting on K-12 school grounds this year, according to CNN's analysis of events reported by the Gun Violence Archive, Education Week and Everytown for Gun Safety.