Mark Kelly, husband of former U.S. Rep. Gabrielle Giffords, listens to Tom Mauser, the father of Columbine High School shooting victim Daniel Mauser, speak during a news conference in

 

              Mark Kelly, husband of former U.S. Rep. Gabrielle Giffords,  listens to Tom Mauser, the father of Columbine High School shooting victim Daniel Mauser, speak during a news conference in
Mark Kelly, husband of former U.S. Rep. Gabrielle Giffords, listens to Tom Mauser, the father of Columbine High School shooting victim Daniel Mauser, speak during a news conference in favor of proposed gun control legislation at the State Capitol, in Denver, Monday March 4, 2013. State Senate committees began work Monday on a package of gun-control measures that already have cleared the House which include limits on ammunition magazine sizes and expanded background checks to include private sales and online purchases. (AP Photo/Brennan Linsley)