A US Capitol police officer responds to a shooting with his weapon drawn as visitor leaves the area at the entrance to the US Capitol Visitors Center March 28, 2016. [Photo/Agencies]

The suspect was undergoing surgery, but his condition was unknown, and no charges have been filed "at this point," Verderosa said.

A US government official said no evidence had materialized of a connection to terrorism.

On a day when the Senate and House of Representatives were not working and few lawmakers were in Washington, the Capitol building was briefly locked down, but then reopened for official business. The Capitol Visitor Center is used chiefly by tourists.

The US Secret Service temporarily cleared tourists from an area around the White House.

At about the same time as the Capitol shooting, a woman was arrested at the White House Easter egg roll because she tried to move a temporary security barrier, the Secret Service said. There was no relation between the Capitol incident and the White House arrest, a Secret Service official said.

The District of Columbia Police Department, a separate force from the US Capitol police, called the shooting an isolated incident and said there was no threat to the public.

More than 2 million people a year go through the Capitol Visitor Center, Verderosa said. He said it would be open for business as usual on Tuesday.