Richard Martinez, whose son, Christopher Michael-Martinez, 20, was gunned down on Friday night in Isla Vista, California, said similar rampages would continue until lawmakers took action on guns.
"We're all proud to be Americans. But what kind of message does it send to the world when we have such a rudderless bunch of idiots in government?" Martinez said on CNN. "I can't tell you how angry I am. It's just awful, and no parent should have to go through this."
Elliot Rodger, 22, the son of a Hollywood director, fatally stabbed three people in his apartment before shooting three people dead near the University of California at Santa Barbara.
He then shot himself. All of those killed were students at the school.
Michael-Martinez, described by his father as articulate and tough, was shot inside a deli. He was the last to die.
Martinez said his son died because Congress had failed to act after a mentally ill gunman killed 26 people in December 2012 at Sandy Hook Elementary School in Newtown, Connecticut.
"These people are getting rich sitting in Congress. And what do they do? They don't take care of our kids," he said.
Legislation after Sandy Hook to extend background checks for gun sales, ban assault weapons and limit magazines' capacities failed to clear the Senate in April 2013. Gun-rights advocates strongly opposed the measures.