U.S. Department of Defense Current Photos via Wikimedia Commons

A home game stunt in recognition of Military Appreciation Day at the Nationals baseball game caused a huge stir which saw the Capital being briefly evacuated.

At the Nationals game on Wednesday, a pregame stunt involving Army Golden Knights parachuting team, who dropped into Nationals Park took the U.S. Capitol by surprise. At around 6:30 p.m. the U.S. Capitol Police sent an alarming notice to Capitol Hill staff that it was “tracking an aircraft that poses a probable threat to the Capitol Complex.” The Capitol was then swiftly evacuated.

Less than 20 minutes later, police sent an update: “The aircraft no longer poses a threat to the Capitol,” and USCP said that buildings in the complex were being prepared for re-entry. Its message did not contain further information about the aircraft police had initially deemed a “probable threat.”

Investigators were still working to determine why the event wasn’t properly coordinated with law enforcement officials in Washington, two people familiar with the matter told The Associated Press. Multiple federal agencies began scrambling officials as the plane circled overhead. Officials believe, based on a preliminary review, the pilot might not have properly reported taking off or had appropriate clearance, the people told The AP.

Kelli LeGaspi, a spokeswoman for the U.S. Army Recruiting Command, which was behind the Golden Knights demonstration, released a statement saying:

“We are reviewing all aspects of the event to ensure all procedures were followed appropriately to coordinate both the flight and the parachute demonstration.”