Ten years ago this spring, two teenagers in Colorado gunned down fellow students and teachers in a killing spree that left 15 dead, 24 injured, and a nation horrified that such carnage could unfold at an American high school. In the decade since, there have been a million gun casualties in the United States. After the Columbine tragedy, I issued a report, "A Farewell to Arms," calling for the country finally to address gun violence head on. I recommended a number of... (GunPolicy.org)