An "improper" mass alert sparked a false report of an active shooter at Walter Reed National Military Medical Center, according to an article on the CNN website.
A Navy's statement attributed confusion to a mistakenly sent notification. Earlier, the Navy and the Pentagon called the incident the result of a drill.
"While preparing for an upcoming drill, the notification system was inadvertently enacted without containing the words 'EXERCISE' or 'DRILL,'" the Navy said.
"Individuals who saw the mass notification statement immediately notified NSA Bethesda security, where they responded accordingly and instituted an installation-wide active shooter response."