Joint Base Andrews, the home of Air Force One, reported an active shooter on its Twitter account.

Somebody messed up. The original post is below.

Joint Base Andrews, in addition to housing the President’s airplane, is also home to the 1st Airlift Squadron, the 459th Refueling Wing, the 89th Airlift Wing, the 79th Medical Wing, the 316th Wing, the 11th Wing, the Air Force District of Washington, and a number of Air Force administrative offices.

The base was supposed to be conducting a drill for an active shooter this morning, coincidentally enough, but the base reports that this incident is not a drill:

More information as we have it.

is now reporting that the drill was in fact responsible for the emergency, but that it was taken too seriously by someone somewhere. Thankfully, no one has been harmed. On the other hand, oops!

:It looks as if the confusion was caused by someone seeing people with guns, who were actually pretending to respond to a pretend incident, according to the local affiliate:

Officials at the base said they were conducting an active shooter exercise at 9 a.m., but around the same time, first responders received reports of an “real-world active shooter situation” at the Malcolm Grow Medical Facility.

Someone on the third floor of the medical facility saw two people walking across the base with long guns. The person didn’t know there was a drill planned and called in the active shooter report, law enforcement officials told NBC News’ Pete Williams.

If you are planning on active shooter drill, please make sure everybody knows beforehand.