Rayburn Building in Washington DC Shuts Down Due to Gunfire

A car may have backfired in the top floor of the Rayburn Building in Washington DC or perhaps some fire crackers, but when an anonymous phone call stated that they heard gunfire; they shut down the Building. Then they locked the doors and shut down the place. But what really happened?

Did someone simply want a 4-Day Weekend since it is a three-day weekend? Sounds like someone is abusing the system and certainly not caring much about their jobs or duty to run the People