UPDATED: June 30, 2016, 10:40 AM ET
Joint Base Andrews, the Maryland home of Air Force One, was put on lockdown Thursday morning after a mistaken report of an “active shooter” during a scheduled security drill, NBC News reported.
A person at the Malcolm Grow Medical Facility who was unaware of the drill saw base personnel carrying long guns and phoned in the report to law enforcement, NBC’s Pete Williams reported, triggering the base’s active shooter protocol.
An “all clear” came from the base’s Twitter account at about 10:40 a.m.
Base personnel were instructed to shelter in place and treated the report as a “real-world active shooter situation” due to its serious nature.
The base was scheduled to conduct an active shooting drill before reports of a “real-world active shooter situation” came in around 9 a.m., the base said on Twitter.
Homeland Security chief Jeh Johnson was made aware of the situation as he testified before a Senate panel and was prepared to leave if need be.
Vice President Joe Biden was scheduled to fly out of the base en route to Ohio but was diverted over the incident.
