The Capitol police announced that the lockdown was over as of Thursday afternoon.
Capitol Police Chief Kim Dine said the incident started at 2:18 p.m., when a vehicle hit the White House gate. Shots were "potentially" fired, before the car fled toward the Capitol building.
Both scenes were secure as of 3:30 p.m., and Dine said, "We have no information that this is related to terrorism." He added that it appears to be an "isolated incident."
Dine said he had no update on the condition of the suspect, though Capitol police believed there was a child in the vehicle.
A police officer was injured during the incident. Dine said the officer was "conscious and breathing."
"As far as we know, no officer has been shot," Dine said.
There were conflicting news reports on the suspect:
ABC News tweeted: #Breaking: Source says female suspect reported dead on scene at U.S. Capitol
NBC News tweeted: Breaking: Female driver tried to ram her car into White House gate. Secret Service chased to Capitol Hill
Bloomberg, meanwhile, reported that a female suspect was in custody, citing Terrance Gainer, the Senate sergeant-at-arms.
President Barack Obama was reportedly briefed on the incident, according to a White House official. Secret Service confirmed that the incident began when a car slammed into a gate at the White House, before fleeing toward the Capitol.
ABC News cited an anonymous source saying the suspect was female and was killed. Law enforcement officials also reportedly found a child in the car, though the child was unhurt.
According to the Associated Press, a police officer was injured during the incident.
"There are reports of injuries," said Gainer, according to the AP. The FBI was also on its way to the scene.
"Shots fired outside the Capitol. We are in temporary lock down," Sen. Claire McCaskill said on Twitter. Police were seen running within the Capitol building and outside as vehicles swarmed to the scene.
House Minority Leader Nancy Pelosi said she heard about the gunshots from Rep. John Lewis, according to Bloomberg.
This was the alert issued by the Capitol police to congressional staff (via Slate):
"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 office’s assigned shelter in place location or the innermost part of the office away from external doors or windows."