SAN FRANCISCO - Authorities said the lone gunman in the school shooting incident in Troutdale, Oregon, in which two were killed earlier Tuesday, was a teenager armed with a rifle.

One student, gunman dead after Oregon high school shooting

Police spokesman Carey Kaer told a press briefing late afternoon that the suspect was spotted slumped on a toilet in a bathroom at Reynolds High School and officers later confirmed he was dead.

"He likely killed himself," Kaer said.

A 14-year-old freshman was found dead in a locker room, and a teacher received treatment at the scene for non-life-threatening injuries.

Authorities said they were withholding the names of the two deceased as they were trying to notify the next of kin for both the slain student and the gunman.

The school, with more than 2,600 students, was locked down after the incident at 8:00 a.m. local time. In TV footage shown on major networks, students were evacuated, walking with their arms raised as they left school buildings.

According to Everytown for Gun Safety, a gun-control advocacy group, the incident in the U.S. Pacific Northwest state is the 74th incident involving guns in schools since the 2012 rampage at an elementary school in Newtown, Connecticut, which left 20 children and six teachers dead.

Troutdale is a small town about 26 km east of downtown Portland. Reynolds is the second largest high school in Oregon.

"This is a very tragic day, one I hoped would never be part of my experience," Reynolds School District Superintendent Linda Florence said at a briefing earlier in the day.