A suspected gunman was wounded in a shooting on Monday on the US Capitol grounds and taken to hospital, police and congressional sources said.
The shooting occurred in the visitors' centre of the sprawling Capitol Complex. The White House was briefly put on lockdown, but that was soon lifted.
Police shot the suspect after he pulled a weapon at a US Capitol checkpoint and a female bystander sustained non-life-threatening injuries, the Associated Press reported.
Speaking to reporters after the incident, Capitol Chief of Police Matthew R Verderosa said the suspect was known to officers.
"We do believe this is an act of a single person who has frequented the Capitol grounds before and there is no reason to believe that this is anything more than a criminal act," Verderosa said.
Initial reports said a police officer sustained minor injuries, but later reports from Capitol officials indicated there was no injury to any law enforcement officers.
The event unfolded with Congress on recess and politicians back in their districts.