How can we prevent mass killings like Aurora?

On the morning of the latest mass shooting, in a place that has become synonymous with tragedy, Tom Mauser's phone rang at 5 a.m. When he turned on the news his first thought was "Oh God," followed by an immediate: "Not again."

He's seen this too often since that April morning in 1999, when his own son Daniel was slain along with 12 others at Columbine High School. In the following years, every time the unthinkable happens yet again — at a Virginia college, a Texas military base, an Arizona strip mall, a Colorado movie theater — Mauser mourns anew.

But he also feels something else, the frustration of seeing the same images again we've seen before.

Any solution is a problem that belongs to each of us, Mauser said.