This was an eyebrow raiser for me. The Washington Nationals had pregame festivities that included the US Army’s premier show jumping team—the Black Knights—parachuting into the stadium. Somehow word of that didn’t get to the DC National Park police. From their perspective, there should not have been an aircraft over the Capital building. Seeing as it was there, though, and not identified by them as belonging to the Army, they had the building temporarily evacuated as a precaution.
The Black Knights perform dozens of show jumps a year, and many, many practices jumps beyond that. They have to have control tower clearance to take off, and their flight plan filed with the FAA prior to take off as well. Being a Black Knight, including being one of the pilots, is a competitive deal—only the best get the assignment. They definitely know the rules. For its part, the FAA does not know where the miscommunication occurred. Obviously there will be an investigation.