Oregon school shooter identified as John Griffin after attack kills 4: Here's what we know

The 16-year-old teenager who killed three children and a teacher at an elementary school in Oregon has been identified as John J. Griffin II, with investigators reportedly believing that the weapon used in the attack was purchased by his mother.

Griffin, a resident of Bend, entered Silver Rail Elementary School on Thursday afternoon after shooting through its locked doors, before opening fire on students and teachers.

According to The Washington Post, which cited two people briefed on the investigation, Griffin was identified as the attacker who was later shot dead by an armed civilian.

One of the sources also revealed that investigators believe the teenager used a shotgun purchased by his mother.

The shooting claimed the lives of three children, aged five, eight and 11, and a teacher. Another seven-year-old student and a 54-year-old teacher were critically injured.

The incident began shortly before 1pm when a driver reported being shot at by someone carrying a long gun.

Within minutes, police received several calls about an armed person entering the school.

But before officers could confront him, a community member who had seen Griffin enter the building followed him inside and fatally shot him.

Bend Police Chief Mike Krantz said officers arrived at approximately 1:02 pm and subsequently confirmed the suspect was dead.

Oregon Governor Tina Kotek praised the civilian for intervening and preventing further loss of life.

Investigators have yet to establish why Griffin targeted the school or whether he had any previous connection to it.