President Obama says his "biggest frustration" in office has been the failure of policymakers to "keep guns out of the hands of people who can do just unbelievable damage."

"We're the only developed country on earth where this happens. And it happens now once a week. And it's a one-day story. There's no place else like this," Obama said during a Q&A at the White House hosted by the social media site Tumblr.

Obama's comments came the same day that a teenage gunman shot and killed a student and injured a teacher inside a Troutdale, Oregon, high school before apparently killing himself, authorities said.

"Why aren't we doing something about this?" Obama said of the recurring violence. "I have been in Washington for a while now and most things don't surprise me. The fact that twenty 6-year-olds were gunned down in the most violent fashion possible and this town couldn't do anything about it was stunning to me."

Obama has called the December 2012 shooting at Sandy Hook elementary school in Newtown, Conn., the "worst day" of his presidency. He launched a campaign to enact legislative reforms, including expanded background checks for gun purchases, but those efforts stalled under stiff opposition in Congress and from the National Rifle Association.

"Most members of Congress - and I have to say to some degree this is bipartisan - are terrified of the NRA," Obama said.

"Until there is a fundamental shift in public opinion in which people say, 'enough; this is not acceptable; this is not normal,'" he said. "Until that's a view that people feel passionately about and are willing to go after folks who don't vote reflecting those values - until that happens, sadly, not that much is going to change."

Obama spoke in response to a question from Nick Dineen, a student at University of California at Santa Barbara and former resident adviser to George Chen, one of the victims of last month's deadly campus shooting that left six students dead.

The president suggested the root cause of so many violent episodes was predominantly easy access to guns rather than mental health issues of the shooter.

"The United States does not have a monopoly on crazy people. And yet, we kill each other in these mass shootings at rates that are exponentially higher than any place else," he said. "Well, what's the difference? The difference is, is that these guys can stack up a bunch of ammunition in their houses and that's sort of par for the course."

Obama said today's shooting in Oregon should, again, prompt "soul searching" nationwide.

(Credit: Olivier Douliery-Pool/Getty Images)