"We are stunned and heartbroken by this senseless tragedy," Steven Cook, the top administrative official of the local school district, said in a statement.

"No words can adequately express the grief our community is experiencing."

Police said the attacker was a local 16-year-old boy, but they did not release any further details on him or the identity of the victims.

Police were alerted to an active shooter at Silver Rail Elementary at 12:59 local time (19:59 GMT), Bend Police Department spokeswoman Sheila Miller told reporters.

The first call came from a person who said that an unknown suspect was shooting into their car with a long gun, police said. Photos released from the scene show a red truck with bullet holes.

Minutes later, the local county dispatch received 911 calls reporting that the attacker had entered the school.

Police said he shot at locks on the doors in order to force his way inside.

Local media reports suggested the school received new classroom doors in 2022 which can be locked with the flip of a switch.

A bystander saw the shooting begin to unfold, pursued the attacker into the school and shot him dead, police said.

Three minutes later, officers first arrived at the scene. They confirmed that the attacker had been killed, and then searched the school.