An Airman assigned to the 56th Security Forces Squadron guards an entryway during an active shooter exercise at Luke Air… https://www.rawpixel.com/image/8741515/photo-image-public-domain-personFree Image from public domain licenseA Team Luke triathlon participant rides her bike during the Luke Triathlon held at Luke Air Force Base, Ariz., Aug. 19, 2017. https://www.rawpixel.com/image/8741594/photo-image-public-domain-personFree Image from public domain license