A man drew a gun while trying to enter the US Capitol visitors centre and was shot by police as panicked tourists fled the scene and the building housing the US Congress was placed on lockdown.
The incident at a screening checkpoint involved a suspect likely known to police, and terrorism was not suspected, Capitol police chief Matthew Verderosa said at a press conference.
The suspect drew a weapon and pointed it at a police officer around 2:39pm on Monday. He was shot by police and was taken to a local hospital where he was undergoing surgery, Verderosa said.
One woman bystander suffered minor injuries during the confrontation.
No police officers were injured, Verderosa said. He said it was unclear how many officers fired shots. A weapon was recovered at the scene and the suspect's vehicle was found on Capitol grounds, the police chief said.
Verderosa said the incident appeared to be "the act of a single person who has frequented the Capitol grounds before". There was "no reason to believe this is anything more than a criminal act," the chief said.
A witness has posted on Twitter, saying: "Was at the Visitors Center... shots heard while going through security, it was a scramble... Capitol evacuated after hiding behind wall."
The Capitol, visitors centre and surrounding congressional office buildings were locked down for about an hour during the busy (northern) spring tourist season when Washington is choked with visitors viewing the city's famous cherry blossoms.
Members of congress were out of town for a recess during the Easter holiday.
The White House, where thousands of families with small children were attending the annual Easter egg roll, was briefly locked down as a precaution.
Emergency sirens were heard across the grassy National Mall between the White House, where the president lives and works, and the Capitol, which houses congress. The two buildings are about 3.4 kilometres apart.
Congressional staff were instructed by the sergeant at arms to stay in their offices.
A shooting at the Capitol in 1998 that left two police officers dead led to the construction of the visitors centre, which is designed to keep visitors at a distance from the building until they undergo security screening.