John Lott, author, More Guns, Less Crime
John DeStefano, mayor, New Haven, Conn.
Pete Earley, author, Crazy: A Father's Search Through America's Mental Health Madness
John Hickenlooper, governor, Colorado
Twenty students and six teachers were killed when a gunman opened fire at Sandy Hook Elementary School in Newtown, Conn. As police continue to investigate the massacre, some argue that it's time to change the conversation about guns in America.