The perpetrator of the Silver Rail massacre has been identified as a 16-year-old teenager

The suspected perpetrator of the shooting at Silver Rail Elementary School in Bend, Oregon has been identified as John J. Griffin II, a 16-year-old resident of the city, according to high-level police sources cited by NBC News. The Bend Police Department, however, has not officially confirmed his identity or revealed a possible motive.

The attack left three children—ages 5, 8 and 11—and a teacher dead. A 7-year-old student and another teacher, aged 54, were seriously injured and were taken to St. Charles Hospital in Bend.

Here's how the attack unfolded

The first 911 call was received at 12:59 p.m. local time, when a person in a vehicle in the parking lot reported that a man armed with a long gun had shot at them several times. Minutes later, other calls reported that the assailant had entered the school.

Bend Police Chief Mike Krantz explained that the teenager forced his way into Silver Rail Elementary by shooting at the locks on the locked doors. The first officers arrived at 1:02 p.m., just three minutes after the first call.

Before police could intervene, a member of the community who saw the assailant enter the school followed him inside and shot him, killing him. Krantz confirmed that officers found the suspect already dead inside the building.

A civilian's intervention

Oregon Governor Tina Kotek praised the man who chased the assailant inside Silver Rail Elementary and put an end to the shooting before police arrived. "To the community member who heroically intervened to prevent further loss of life: your actions carry a very heavy emotional burden and I want you to know that my thoughts are with you as well," she said.

The Bend Police Department has not officially confirmed the identity of the person who intervened and has referred to him only as a "community member." Some media outlets, including NBC News, have reported that he may be Kaylub Giamanco, a 36-year-old carpenter and father of two students at the school, according to his brother's account.

The weapon and unanswered questions

A law enforcement official told The Associated Press that the shooter used a pump-action shotgun that had been purchased by his mother. The Bend Police Department has not officially confirmed that detail nor has it explained how the minor gained access to the weapon.

Authorities also have not determined whether Griffin had any prior connection to the school, to any of the victims, or to the facility. The FBI and the ATF are collaborating on the investigation, which remains open.