Students walk to board a bus amid heavy police presence at the Evergreen Library after a shooting at Evergreen High School in Evergreen, Colo., on Wednesday. (Hyoung Chang/The Denver Post via AP)

DENVER (AP) — A 16-year-old boy who had been radicalized by an unspecified “extremist network” fired a revolver multiple times during an attack at a suburban Denver high school that wounded two students, authorities said Thursday.

Some students ran and others locked down during Wednesday’s shooting at Evergreen High School in the foothills of the Rocky Mountains. One of the victims was shot inside the school and another outside.

The suspect in Evergreen, student Desmond Holly, shot himself at the school and later died, said Jefferson County sheriff’s office spokesperson Jacki Kelley. The county was also the scene of the 1999 Columbine High School shooting that killed 14 people.

The school resource officer was on medical leave and two part-time officers who now share the job were not present at the time, she said at a news conference. The officer working at the school that day had been sent earlier to a nearby accident.

Kelley said Holly had been “radicalized by some extremist network,” and suggested authorities came to that conclusion after examining the suspect’s home and phone.

But details on how he allegedly had been radicalized and by what group were not immediately released, with Kelley promising more information at a later date.

It also remained unclear if Holly knew the victims and had a dispute with them, or if they were shot randomly. Both were reported in critical condition Thursday.

Officials released a statement from the family of one of the victims, Matthew Silverstone, 18, expressing appreciation for the support they’ve received and requesting privacy as the family focuses on his recovery.

The other victim had not been publicly identified.

Kelley described a chaotic scene as the students sheltered in place or fled the 900-student campus, about 30 miles (50 kilometers) west of Denver.

“He would fire and reload, fire and reload, fire reload,” she said. “This went on and on.”

But the shooter was blocked by secured doors and couldn’t get into areas where students were sheltering, Kelley said. She added that Holly had lots ammunition.

“The reason we have so many crime scene areas inside is because we have windows shot out. We have lockers that were shot up. We’re finding spent rounds, unspent rounds. So it’s a huge area,” she said.

Investigators were searching the suspect’s room, his backpack and his locker. They also were in contact with the suspect’s parents.

Kelley said authorities would be looking at whether the parents should face any criminal charges for allowing him access to the gun.