The U.S. Capitol was briefly evacuated Wednesday after police identified an aircraft that they said posed "a probable threat."

The plane was actually carrying members of the U.S. Army Golden Knights, who then parachuted into the Washington Nationals' baseball stadium for a pregame demonstration.

Nationals Park is located a little more than a mile from the U.S. Capitol.

The alert from the U.S. Capitol Police sent congressional staffers fleeing from the Capitol and legislative building around 6:30 p.m.

Investigators were still working to determine why the event wasn't properly coordinated with law enforcement officials in Washington, according to sources.