A police officer and a suspect were wounded Thursday outside the U.S. Capitol, which was locked down for about 45 minutes after unconfirmed reports of shots fired.
"This appears to be an isolated incident" unrelated to terrorism, U.S. Capitol Police said at a briefing.
Police said they are investigating multiple crash locations. One crash occurred at 1st and Constitution Avenue, where the officer was injured but appeared to be conscious and breathing while being transported to a local hospital. The other crash happened at 2nd and Maryland Avenue. A woman was injured as well.
A Capitol police cruiser had been abandoned in the street, its driver-side door open and the air bag deployed. A rear door had been ripped from its hinges and was lying in the street.
D.C. Police and the U.S. Secret Service are involved in the investigation.
President Barack Obama was briefed on the reports of gunfire on Capitol Hill this afternoon. White House staff are in touch with law enforcement and are monitoring the incident.
Shortly after the reports of shots fired at the Capitol, the Secret Service began putting up metal barricades along Pennsylvania Avenue outside the White House and herding tourists off the sidewalk and into nearby Lafayette Park.
Few knew what was happening and tourists began to congregate, taking pictures of the officers on horseback and as police began moving the barricades into place.
Rep. Juan Vargas, D-Calif., told McClatchy he was walking on 1st Street toward the Capitol when he heard a "pop, pop." A police officer then ran up to him, telling him to stop where he was.
"He told me to take the pin off," said Vargas, referring to his U.S. Congress lapel pin, "and I said 'What's going on?' and he said: 'Two officers shot, two officers down. Take your pin off, you could be a target.'"
During the lockdown, McClatchy's William Douglas reports, news crews were running toward the Hart Senate Office Building, which is near the Supreme Court building. People, mainly tourists, were seen running from Amtrak's Union Station toward the Capitol.
Police outside the Hart Building were scurrying, some with rifles in hand but pointing toward the ground.
At 2:25 p.m. ET, Capitol Police sent an alert:
"SHELTER IN PLACE. Gunshots have been reported on Capitol Hill requiring staff in all Senate Office Buildings to immediately shelter in place. Close, lock and stay away from external doors and windows. Take annunciators, emergency supply kits and escape hoods; and move to your offices assigned shelter in place location or the innermost part of the office away from external doors or windows. If you are not near your office, go to the office nearest to you and shelter with that office and then check in with your OEC. No one will be permitted to enter or exit the building until directed by USCP. Staff is advised to monitor the situation. Further information will be provided as it becomes available."
David Lightman, Michael Doyle, Mark Seibel, Anita Kumar, Lesley Clark, Sarah Sexton, and Kendall Helblig contributed to this report.