A rifle-toting gunman killed a 14-year-old student at an Oregon high school Tuesday, the latest in a spate of US shootings that prompted a renewed warning from President Barack Obama.

The gunman, said to be another student, also died in the shooting at Reynolds High School in the northwestern US state, taking his own life according to media reports.

Police named the victim as Emilio Hoffman, who died in a boys' locker room of the school's gym building. The shooter, who has still been identified, was found in a separate bathroom.

Troutdale Police Chief Scott Anderson praised the actions of two school resource officers who were among the first to respond to the shooting.

"I believe their quick response saved many of our students' lives," he said, while not confirming whether the shooter had killed himself or been shot.

Witnesses reported students and teachers cowering in classrooms as the shooting unfolded. One teacher also suffered non life-threatening injuries, police said.

As the drama unfolded, live TV pictures showed the increasingly common sight of students filing out of the school with their hands on their heads.

"My daughter was just shaking and scared," said one mother.

"She was huddled in the corner of a room with some students and had the lights out," she told KOIN 6 television.

"When a SWAT team person unlocked the door to her room she freaked out, thinking that it was the shooter coming in," the mother, identified as Becky, told the broadcaster.

Anderson added that, during the school search, another gun was found, and its owner taken into custody. He stressed that this appeared totally separate from Tuesday's shooting.

This was the fourth shooting in three weeks in the former Wild West region of the United States.

Epidemic of gun violence

On May 23, a student with mental problems, the son of a Hollywood director, went on a gun rampage at a college campus in Santa Barbara, north of Los Angeles, killing six people and then himself.

On June 5, a gunman killed one person and injured two others on on a college campus in the northwestern US city of Seattle, in what the local mayor denounced as America's "epidemic of gun violence."

Then on Sunday, a couple with possible links to anti-government militia shot dead two police officers execution-style in a Las Vegas pizza restaurant, before killing another civilian nearby and then themselves.

Previous mass shootings, like that which killed 20 children and six adults in Newtown, Connecticut in December 2012, have triggered intense debate about America's relatively lax gun control laws.

But the latest wave had triggered only muted public debate, possibly due to the scale and regularity of the killings or the the lack of concrete progress generated by previous protests.

President Barack Obama changed that Tuesday, launching a heart-felt lament that such attacks were "becoming the norm" -- and dismissing the argument shootings were primarily a mental health issue.

"The United States does not have a monopoly on crazy people," the president said during a Tumblr online forum.

"It's not the only country that has psychosis, and yet we kill each other in these mass shootings at rates that are exponentially higher than any place else.

"What's the difference? The difference is that these guys can stack up a bunch of ammunition in their houses."

The school where Tuesday's shooting occurred has some 2,800 students, although many of them finished classes last week, so it was unclear how many were on site.

National and local TV news channels covered the scene live, showing large numbers of armed police scrambling to lock down the school after reports of shots fired around 8:00 am.

But about an hour later, the Multnomah County Sheriff's Office said the situation was "stabilized."