(CNN) – Eleven years ago today the Columbine High School massacre was set in motion when four high-powered weapons were bought at a gun show without a background check. A group of the nation's mayors now wants to close the so-called "gun show loophole" that side-steps background checks and record keeping.
The group "Mayors Against Illegal Guns" is launching a full-scale media offensive trying to convince Congress to rewrite gun show laws. One of the group's leaders is New York City Mayor Michael Bloomberg and he joined us exclusively on Tuesday's American Morning to discuss their efforts.