The unidentified man fled authorities, hitting one officer who was injured, said Sgt. Kim Schneider, U.S. Capitol Police spokeswoman. The 35-year-old man was shot after being told to put down his weapon and refusing, Schneider said.
The late afternoon melee happened a few blocks from where the third day of hearings for Supreme Court nominee Sonia Sotomayor was wrapping up. Police briefly sealed off part of the Capitol as a precaution, but the complex was reopened shortly afterward.
Authorities said the incident was unrelated to the Capitol complex.
"There were so many gunshots being fired my family got down," said Robert Drumm, a tourist from Oklahoma who was visiting the nation's capital with his family.
He said he saw someone being taken away in an ambulance. He said he first noticed trouble when he saw one car speeding and being chased by a police vehicle.
Numerous emergency vehicles converged quickly in the area.
Another witness, Dale Lanigan of Toledo, Ohio, described a similar scene, although he said two police cars gave chase.
As the car went past him, Lanigan said, "the driver had one hand on the wheel and it looked like he was reaching for something."
Lanigan said he then heard shots and police ordered him to get away. He said the driver of the car was taken away in an ambulance.