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In this image taken on a cell phone, authorities gather outside Torgersen Hall on the Virginia Tech campus in Blacksburg, Va., Thu Police officers block a road on the Virginia Tech campus in Blacksburg, Va., after a gunman killed a police officer Thursday, Dec. A police officer secures the scene where a gunman killed a police officer after a traffic stop Thursday, Dec. 8, 2011 on the campu A police officer secures the scene where a gunman killed a police officer after a traffic stop Thursday, Dec. 8, 2011 on the campu