“Senator Reid asked the officer how he was doing, and the officer said he’s going to be fine,” Mr. Reid’s office said. “The officer said to Sen. Reid, ‘The only thing I do every day is to make sure you and everyone who works up here is safe.’”
Inside the Capitol, lawmakers offered a sustained bipartisan standing ovation after House Minority Whip Steny H. Hoyer, Maryland Democrat, expressed his gratitude to Capitol Police.
Outside the building, the fast-moving chase and the gunshots shook tourists and government workers alike.
Ryan Christensen of Idaho Falls, Idaho, said he was walking toward the west front of the Capitol when he saw the black car speed out of the roundabout.
“That’s when the shooting started,” he said. He and a friend took cover in the grass.
“We couldn’t really pay attention. We were trying to hide from stray bullets,” Mr. Christensen said.
Alan and Faith Silverman, visiting from Diamond Bar, Calif., were sitting on the East Lawn of the Capitol taking pictures when they heard six pops to their left.
“Then I heard what sounded like automatic gunfire, and I told my wife we should get up and move,” Mr. Silverman said.
Almost immediately, police ran across the lawn shouting at everyone to run if they were able, his wife said, impressed by the swift response. “We walked real fast — we’re too old to run,” she said.
Rep. Gerald E. Connolly, Virginia Democrat, and Rep. Matt Cartwright, Pennsylvania Democrat, were having a conversation on the balcony outside the House chamber when they heard two bursts of about seven or eight rounds of gunfire.
“We were like, ‘What is that?’ ” Mr. Connolly said. “I thought it was fireworks.”
Then officers waved for them to go inside.
At one point, an officer was crouched with a rifle to his shoulder, guarding visitors he had gathered and had crouching behind a stone wall near the Capitol.
A notice broadcast on the internal television system ordered employees to “close, lock and stay away from external doors and windows.”
Minutes after the alert was issued, police had barricaded off Constitution Avenue and shut down the grounds.