Adam Lanza kills 20 first-graders and 6 staff at Sandy Hook; Senate background check bill fails

Adam Lanza, 20, killed his mother at their Newtown, Connecticut home, then drove to Sandy Hook Elementary School, where he fatally shot 20 first-graders and 6 staff members on December 14, 2012, using a Bushmaster XM-15 semiautomatic rifle and 30-round magazines. Principal Dawn Hochsprung and school psychologist Mary Sherlach died confronting Lanza before he entered classrooms. The attack lasted approximately 11 minutes before Lanza killed himself. President Barack Obama called the shooting "heartbreaking" and vowed action, but a Senate bill imposing universal background checks failed 54-46 in April 2013, short of the 60-vote threshold needed to overcome a filibuster.