A US Capitol Police officer has been shot near the Capitol Visitor Centre complex.
Reports suggest the officer was not seriously injured during the incident.
The event unfolded with Congress on recess and politicians back in their constituencies.
It occurred in the visitors' centre of the sprawling Capitol complex.
Staffers, reporters and others were told to "shelter in place" and not allowed to leave their offices. The White House and the Capitol complex were put on lockdown.
A suspect was taken into custody, Capitol officials and police said.
"There has been an isolated incident at the US Capitol. There is no active threat to the public," the DC Police Department tweeted.
In a reportedly unrelated incident a man attempted to jump the fence surrounding the White House.
This is a developing story and will be updated