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 anther outside.

The suspect, student Desmond Holly, shot himself at the school and later died, officials with the Jefferson County sheriff’s office said.

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

Sheriff’s office spokesperson Jacki Kelley said during a news conference that 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. Kelley said more information would be disclosed at a later date.