U.S. Air Force Col. Randall Sparks, the 509th Mission Support Group commander, salutes a battlefield cross after placing a rose in a boot to recognize a fallen law-enforcement member, at Whiteman Air Force Base, Mo., May 16, 2016. Every 20 minutes between reveille and retreat on the day of the vigil, volunteers recognized an officer who died in the line of duty for their sacrifice. (U.S. Air Force photo by Airman 1st Class Michaela R. Slanchik)