Summary: Headlines for December 17, 2012; "We Can't Tolerate This Anymore": Obama Vows Action After Worst Grade School Massacre in U.S. History; Debate: After Newtown, Will Nation's Worst-Ever Grade School Shooting Spur Tougher Gun Control?; Egypt's Referendum Clears 1st Round, But Critics Seek Revote After Charges of Rigged Polls
