Families have been torn apart and Good Samaritans honoured as fresh details emerge after a teenager opened fire at an elementary school in the US.

Police have revealed 16-year-old Griffin J. John II was armed with a pump-action shotgun when he entered Silver Rail Elementary School in Bend, Oregon, and opened fire about 1pm on Thursday, local time.

John fired as many as 15 rounds into a special education classroom, killing three students, aged 5, 8 and 11, and a 25-year-old teacher.

Know the news with the 7NEWS app: Download today

Another teacher and a seven-year-old student remain in hospital with critical injuries.

The horrific ordeal lasted just two minutes and was brought to an end after a carpenter ran towards danger before shooting John dead.

The details were revealed by local officials during a press conference on Friday, local time, as the FBI-aided investigations piece together what led to the shooting.

Bend-La Pine schools Superintendent Steven Cook said John used to be a special needs student at Silver Rail Elementary, which Bend Police Chief Mike Krantz said was the target of the attack.

Police have identified the 16-year-old who shot and killed three students and a teacher at Silver Rail Elementary School in Bend, Oregon. Credit: Haven Daley/AP

Family heartbreak after victims identified

Kelik Summer took to social media hours after the shooting to confirm her son, five-year-old Rhoam Summer, was one of the victims.

Be the first to know:

“(Today was) the worst day of my life,” she said, adding: “My son Rhoam was killed in a school shooting.”

“We are broken and lost, but are surrounded by friends and family who are keeping us safe.”

Five-year-old Rhoam Summer has been identified as a victim of the shooting. Credit: Swan Amity

The family of 25-year-old teacher Megan Lambert have also come forward following the tragedy, saying she lived to teach.

“She loved Silver Rail,” her family said in a statement read during Friday’s news conference.

“This was her dream job.

“She always fought for the underdog and those with special needs.”

Lambert was a Central Oregon native who graduated from Boise State University in 2023 and coached girls in the Central Oregon Volleyball Club, the family said.

She also loved volleyball, and turned down pay during her first season at the club so girls who normally couldn’t afford the costs of participation could play.

She was a substitute at Silver Rail Elementary School before becoming a full-time teacher, the family said.

Hundreds of locals attended a candlelight vigil for those killed and injured in the attack. Credit: Eli Imadali/Oregon Public Broadcasting via AP

Presidential praise for Good Samaritan

Carpenter and father, Kaylub Giamanco, was driving home from lunch when he overheard the shots and saw the gunman enter the school where his two daughters attend.

The 36-year-old jumped into action, grabbing his 40-caliber pistol “and decided to go in after” the shooter, his brother Kyle Giamanco recounted to NBC.

Bend Police Chief Krantz said a teacher was the first to confront John, throwing her phone at the teenager and tackling him after he stormed the classroom.

She fought to disarm the shooter and bought time for Giamanco to locate and shoot the teenager multiple times.

Kaylub Giamanco overheard gunfire and ran towards danger before shooting and killing the 16-year-old gunman. Credit: Facebook

Krantz said the teacher was miraculously uninjured during the incident and was “almost certainly help prevent more bloodshed”.

Both she and Giamanco have been praised for their actions, with the carpented being recognised by US President Donald Trump.

“As bad as it was, we had a great hero that went in and ... took care of business,” Trump told reporters on Friday.

Kyle described his brother as a hero, but doesn’t want to speak out right now is because he doesn’t feel like he is one, adding Giamanco can’t get the children out of his head and feels guilty he didn’t save more people.

Cops claim mother purchased gun used in shooting

Police returned to the school on Friday as part of ongoing investigations into the motive behind the attack, Bend Police Chief Krantz told reporters.

He revealed the shotgun used in the attack was bought by John’s mother in August and used three types of ammunition: birdshot, buckshot and slugs.

Police arrived on the scene to find the 16-year-old dead, with a gun and backpack containing 44 more rounds of ammunition nearby.

Investigators are trying to figure out how he got a hold of the firearm and ammunition, and have executed a search warrant at his home.

Roughly 150 law enforcement and first responder personnel have been involved in the investigation, including Oregon State Police, the FBI and the ATF.

— with NBC