The 633d Security Force Squadron at Langley Air Force Base, Va., wears black tape over their shield in mourning for Senior Airman Nicholas J. Alden,who was killed en route to Afghanistan March 2, 2011. The display is a time-honored tradition within the law enforcement community, as a symbolic gesture for officers killed in the line of duty. (U.S. Air Force photo byAirman 1st Class Jason J. Brown/RELEASED)