Why do some people commit mass shootings?
Published On: Jul 20 2012 05:21:06 PM CDT
Updated On: Jul 20 2012 05:54:29 PM CDT
July 20, 2012: From Columbine to Virgina Tech, Fort Hood to Tucson, the rampages were unexpected and impersonal. A Houston psychologist says behind them all are accused shooters who had an overriding emotion. Amy Davis reports.