Ian Mercer, during an interview outside his California home Saturday, told CNN that he didn't know his son had a single gun, let alone 13. He asked, "How on earth could he compile 13 guns? How could that happen?"
Mercer's son, Chris Harper-Mercer, staged an attack at Umpqua Community College, killing nine people and injuring nine others Thursday.
During his interview, Ian Mercer appeared to walk back his statement that guns were to blame, but only briefly.
"We talk about gun laws. We talk about gun control. Every time something like this happens, they talk about it and nothing gets done. I'm not trying to say that that's to blame for what happened, but if Chris had not been able to get hold of 13 guns, this wouldn't have happened," the father said.
Mercer said he has never held a gun. He doesn't want to, he said. He laid out his personal philosophy on the issue: "I'm a great believer (in) you don't buy guns, don't buy guns, you don't buy guns."
Other countries don't see mass shootings at the same clip that the United States does, he said, asserting, "Somebody has to ask the question: How is it so easy to get all these guns?"
His condemnation of guns grew stronger as the interview went on, and he closed his remarks on the subject with a call for change.
"It has to change. How can it not? Even people that believe in the right to bear arms, what right do you have to take people's lives? That's what guns are, the killers. Simple as that. Simple as that. It's black and white. What do you want a gun for?"
Pressed on whether his son's mental state could be to blame for the violence, Mercer declined to comment, saying he wanted to let police follow through, but he left open the possibility that his son's state of mind could have played a role.
"Obviously, somebody who goes and kills nine people has to have some kind of issue. Whatever it is, let the police determine what they find," he said.