A 16-year-old teenager who broke into an elementary school in the western U.S. state of Oregon opened fire during daytime classes, killing four people, including three children and a teacher.

The gunman was also shot and killed by a citizen who witnessed the crime and pursued him into the school.

Around 1:00 p.m. local time on the 15th, an intruder entered Silver Rail Elementary School in the central Oregon city of Bend and began shooting.

Authorities found that the suspect first fired shots at a vehicle parked outside the school before entering the building.

Police stated that the gunman gained entry to the school building by shooting at a locked door.

Aside from the fact that he is 16 years old, specific identification details have not been released.

The motive for the crime, including what relationship the gunman had with the school, remains unknown.

The deceased include three elementary school students aged 5, 8, and 11, along with one teacher.

Separately, another 7-year-old student and a 54-year-old teacher were reportedly rushed to the hospital with severe injuries.

Police reported that a citizen who witnessed the gunman entering the school chased after him and shot him dead.

The identity of this citizen has also not been released yet.

Police explained that they arrived at the scene within three minutes of receiving a report that "a person has entered the school and started shooting," but the suspect was already dead from the citizen's gunfire.

Oregon Governor Tina Kotek, who attended the briefing, expressed gratitude to the citizen, stating, "His heroic intervention prevented further loss of life."

Bend, where the shooting took place, is a rural community with a population of about 100,000.

The Bend-La Pine Schools district, to which the affected school belongs, has currently placed schools on lockdown.

Superintendent Steven Cook released a statement saying, "We offer our condolences to the bereaved families and everyone affected," adding, "Our immediate priority is to care for students and staff and to support law enforcement and emergency responders."

Silver Rail Elementary School, which serves grades kindergarten through fifth, has a total enrollment of 462 students, of whom 80% are white and 20% belong to low-income families, according to the local newspaper The Oregonian, citing state government data.

(Photo: AP, Yonhap News)