Across the Nation

President Barack Obama answers a question during a Tumblr forum, moderated by Tumblr founder and CEO David Karp, left, Tuesday, June 10, 2014, in the State Dining Room of the White House in Washington.  (AP Photo/Jacquelyn Martin)

“My biggest frustration so far is the fact that this society has not been willing to take some basic steps to keep guns out of the hands of people who can do just unbelievable damage,” Obama said.

Jose Cardoso pays his respects at a makeshift memorial in front of the IV Deli Mart, where part of Friday night's mass shooting took place by a drive-by shooter Sunday, May 25, 2014, in the Isla Vista area near Goleta, Calif. (AP Photo/Chris Carlson)

Mass murderers tend to have a history of pent-up frustration and failures, are socially isolated and vengeful, blaming others for their unhappiness, experts say.