'Hero' bystanders helped prevent further bloodshed in deadly Oregon shooting

Authorities investigating the fatal shooting that claimed the lives of three children and a teacher in Oregon have hailed a father and a teacher who intervened as heroes.

Speaking to the media a day after the tragic shooting at an elementary school in Bend, Police Chief Mike Krantz praised the actions of several bystanders who "intervened to prevent this tragedy from being any worse".

"We owe you a debt of gratitude," he said.

Chief Krantz said the 16-year-old shooter, identified as Griffin J John II, a former special needs student at Silver Rail Elementary, was shot dead by a man whose children also attend the school in Bend.

Police say just before 1pm on Thursday, local time, the teen was observed throwing a gun over the school's gates and scaling the fence.

Chief Krantz said a witness confronted the gunman, who shot a number of rounds at their car before continuing towards the school. The witness called 911 shortly after.

A 36-year-old father with two children attending the school witnessed the initial shooting and pursued the teen armed with his "legally secured" pistol, Chief Krantz said.

He entered the school and found the 16-year-old struggling with another teacher before firing multiple rounds at the teen, killing him.

The police chief did not identify the teacher who fought the assailant, but told the press conference she threw her phone at the suspect, tackled him and fought to take his shotgun from him.

"She was not injured in that incident, but she almost certainly helped prevent more bloodshed," Chief Krantz said.

Initial investigations have determined the teen had gained entry into the school by shooting the glass panes in the doors.

He went into a classroom, identified as a special needs class, and fired up to 15 rounds using a 12-gauge pump-action shotgun, killing three children and one adult.

"All of the victims were shot in that classroom," Chief Krantz told reporters.

A 25-year-old teacher and Oregon local, Megan Lambert, was identified as the adult killed in the shooting.

Her family provided a statement to police, which was read to reporters at a press conference on Friday.

"Silver Rail was her first job as a teacher," the statement read.

"Megan loved those children," it said.

The youngest victim, identified with the permission of his family, was five-year-old Rhoam Summer.

Two boys aged eight and 11 were also killed.

A seven-year-old girl remains in a serious but stable condition, while a 54-year-old female teacher suffered serious but non-life-threatening injuries.

Chief Krantz said police are yet to confirm a motive and how the 16-year-old came into possession of the gun.

He said a further 45 rounds of ammunition were found in a backpack belonging to the teen and found nearby.

Holding back tears, he said: "Please hold the victims of this tragedy, the families and your community in your hearts with me."