BEND, Oct 16 — A teenager shot and killed three children and a teacher yesterday at an elementary school in the US state of Oregon, police said, adding the assailant was later killed by an armed bystander who pursued him into the building.

Officers rushed to Silver Rail Elementary in Bend, a city of about 100,000 in the nation’s northwest, after reports of a shooter on campus yesterday afternoon.

The three children who died on the scene were aged five, eight and 11, said Bend police chief Mike Krantz. Another child and a teacher were being treated for critical injuries after the shooting.

The United States, where firearms are readily available, has a long and painful history of gun violence, with thousands of people killed every year. It has the highest rate of gun-related deaths among all developed nations.