There were reports of an active shooter incident at Walter Reed hospital today which confused and frightened people. Officials later clarified that the situation was only a drill. Rep. Dutch Ruppersberger was at the hospital when the reports first went out and tweeted this:

People inside were sheltering in place:

Montgomery County police said they were responding to the incident:

Local news reporters were reporting it as an active shooter situation:

But authorities eventually said the entire situation was a drill:

The Washinton Post reports it was an “ad hoc drill.”

About an hour after a report of an incident at Walter Reed Authorities brought police swarming to the facility Tuesday afternoon for a possible active shooter , the U.S. Navy said the event was “an ad hoc drill” by the command there.

Not everyone was pleased with that explanation:

Naval Support Activity, which responded to the incident, described it as a false alarm:

And one of the people trapped inside said they had no idea it was a drill and that it was described to her as a mistake:

How does all of this make sense? The Hill reports that this was in fact a drill that was intended to take place in a part of the hospital that was empty but, for some reason, security wasn’t notified in advance:

A Navy official told The Hill that it was a scheduled active shooter exercise by tenant command of NSAB, in a section of the hospital where there are no patients.

The tenant command did not notify the installation of the exercise ahead of the drill, which took place in Building 19, or the America Building.

The official said the building’s security would normally be notified but were not this time. They could not give a reason for why Walter Reed personnel were not informed.

Obviously, it’s a relief that this wasn’t a genuine active shooter incident, but I think Fox News’ Jennifer Griffin is right that someone owes the people who were terrified about what was happening an apology: