On Sunday, CNN spoke with Ian Mercer, the father of the 26-year-old gunman who killed nine people and wounded nine others at Umpqua Community College in Roseburg, Oregon. Mercer said he was taken aback after investigators discovered that his son had an arsenal of 13 firearms—six of which were found on his person during the tragedy on October 1. 

"How on earth could he compile 13 guns? How can that happen?" Mercer's father asked. "They talk about gun laws, they talk about gun control. Every time something like this happens, they talk about it, and nothing is done."

For many, the fact that the U.S. accounts for approximately one-third of the mass shootings that happen globally (despite having only five percent of the world's population) is a troubling indictment of our nation's gun policies. And though Mercer said he understands that America's relatively lax gun control policies are "not to blame for what happened," he also stated that his son shouldn't have been able to obtain that number of firearms. 

"[I]f Chris had not been able to get ahold of 13 guns, it wouldn't have happened," he said bluntly. 

"You don't see these kinds of mass shootings all over the world on a consistent basis like you do in the United States, so somebody has to ask the question: how is it so easy to get all these guns?" he added. "How was he able to compile that kind of arsenal?"

CNN followed up by asking Mercer if he believed that gun laws should change in America. The father of the shooter left no room for interpretation: "It has to change," he said. "How can it not?" 

"Even people that believe in the right to bear arms... you know, what right do you have to take people's lives? That's what guns are to killers. It's as simple as that." 

The powerful interview comes three days after the gunman opened fire at the Oregon community college—a tragedy that prompted President Obama to call for renewed efforts to pass gun control legislation.