Oregon school shooter who killed three children and a teacher named as John J. Griffin, 16, as it's revealed he also shot seven-year-old in wheelchair

A teenage school shooter who murdered four at an elementary school has been named as John J Griffin.

Griffin, 16, killed three children aged five, eight, and 11 at Silver Rail Elementary School in Bend, Oregon, on Thursday afternoon.

He also critically wounded a 54-year-old teacher and shot a seven-year-old child who uses a wheelchair in the face, both of whom are still in hospital.

The teen killer began firing after entering a special education class. It is unclear if it was specifically targeted or chosen at random.

Griffin was shot dead minutes after he began his rampage by Kalub Giamanco, 36, a dad of two children at the school who heard the gunshots as he drove home for his lunch break.

Giamanco's wife Kelsey and brother Kyle, along with several of his friends, confirmed he was the hero who intervened by running inside the school.

He holds a concealed carry permit and is friends with the family of the seven-year-old in the wheelchair who was wounded.

The first victim of the shooting has been named as a five-year-old boy called Rhoam Summer.

Griffin used his mother's pump-action shotgun to carry out the massacre, which police said was bought about the time of Griffin's 16th birthday.

He used it to blast his way through a 'safety vestibule' system designed to keep children safe from school shooters. 

Police raided Griffin's family home on Thursday night, seizing computers and other electronic devices. His parents were said to be cooperative.

Giamanco shot Griffin dead within moments of the massacre beginning just before 1pm on Thursday.

A motive for the killings has yet to emerge.  

More to come.