On July 20, 2012, twelve people were killed and seventy wounded at a mass shooting in a movie theater in Colorado. In 1999, twelve kids and one teacher at Columbine High School were murdered by two students. In 2012, twenty children and seven adults were killed at Sandy Hook Elementary. Thirty-two were killed at Virginia Tech. Twelve killed at the Washington Navy Yard. In May 2014, after posting a YouTube video of “retribution” and lamenting a life of “loneliness, rejection, and unfulfille...