A chaotic car chase that began when a woman tried to ram a security barrier near the White House ended with shots being fired near the U.S. Capitol, putting the Hill temporarily on lockdown and causing what one witness described as "mass panic." 

According to U.S. Capitol Police, one officer was injured in a related car crash.

The chase and subsequent stand-off near the Capitol went down as lawmakers were debating under the dome about the partial government shutdown. Officials say the incident was not related to terrorism, and the suspect is in custody.

One person could be seen being carried off in a stretcher -- it's not clear if that was the officer in question. It's also not clear who fired the shots.

Terrance Gainer, the Senate sergeant at arms, told Fox News that this appears to be an "isolated incident." Gainer also said the officer injured crashed a police cruiser while trying to join the chase. The cruiser "seriously clipped" a barricade, he said, but the injuries are "not life threatening."

The chase and stand-off caused panic on Capitol Hill, with sirens blaring inside the building and lawmakers and their staff being ordered to stay in place. The lockdown has since been lifted, and those inside the Capitol are no longer being ordered to "shelter in place."

Sources told Fox News the incident began with a car chase, which started when a woman tried to ram a gate near the White House.

Several police cars pursued her to a location near the Capitol building. When they boxed her in, sources said, the driver got out and five or six shots were fired. Witnesses saw a baby being taken from the car.

Eyewitnesses described a chaotic scene.

"We were definitely caught off guard, we were scared," said Matt Knuppeo, who said he was touring the Capitol building when the stand-off unfolded. "It was mass panic for a while."

"We just heard the gun shots -- pow pow pow pow," witness Emily Wheeler told Fox News.

The developments come as lawmakers were debating a series of small spending bills, amid the ongoing partial government shutdown.

The violence follows the mass shooting last month at the Washington Navy Yard.