Police in Bend, Oregon, on Friday identified the teenager who attacked Silver Rail Elementary School a day earlier as a former special-needs student of the school, in an update reported by Reuters and Al Jazeera. The 16-year-old killed three children, aged five, eight and 11, and a teacher before he was shot dead by a parent who followed him inside.

Bend Police Chief Mike Krantz told reporters the attacker forced his way through locked doors with a shotgun and fired multiple rounds, and that he still carried dozens of rounds when he died. Investigators searched his home, seized electronic devices and are still working to establish how he obtained the gun, which reports say was registered to his mother.

Officials praised the response inside the school. A teacher confronted and fought the gunman after throwing her phone at him, actions the police chief described as heroic and likely life-saving, while a father of two pupils at the school pursued the attacker and shot him minutes after the first emergency call. A seven-year-old pupil and a 54-year-old teacher remained in hospital in critical condition.

Oregon's governor called the parent's intervention heroic, and the attack has again revived debate in the United States over gun access and school safety. Police say the investigation will be long, and the school community in Bend, a city of about 100,000, faces days of mourning and support work ahead.