SCHRIEVER AIR FORCE BASE, Colo. (AP) -- Air Force officials say an airman armed with a pistol has barricaded himself in a building at a Colorado Air Force base that controls all GPS satellites, but operations haven't been disrupted. Schriever (SHREE'-ver) Air Force Base spokeswoman Jennifer Thibault (THEE'-balt) says the building was evacuated after the standoff began Monday. She says no shots were fired and no one was injured.