The United States Capitol was placed on lockdown for a half-hour Thursday afternoon after a woman tried to ram a car into the White House gate, was chased by Secret Service and shot and killed by police, sources said.

The suspect — who sources said had a child in the car — may have fired on law-enforcement, sources said. At least one Capitol Police officer was injured, but not shot, during the pursuit, officials said.

Dramatic video showed officers with guns drawn surrounding the woman’s black sedan before she suddenly sped away. Several shots could then be heard as cops took off after the car.

“This appears to be an isolated incident,” said Capitol Police Chief Kim Dine. “Both scenes are under control.”

President Barack Obama was briefed about the harrowing incident, which came in the midst of the government shutdownthat has created a tense atmosphere on Capitol Hill.

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It started at 2:18 p.m. when the woman in a black car tried to breach White House security at 15th St. and E, law-enforcement sources said.

She did not get through and was chased at high speeds for about 12 blocks, the sources said.

Her car hit a Capitol Police vehicle at Second St. and Constitution Ave. and then crashed into barricades a few blocks away, Dine said. The child was reported to be safe.

The woman’s motive was unknown but Dine said there was no reason to think it was an act of terrorism.

Travis Gilbert, who watched the chase from the roof of the Newseum, said vehicles involved “had several close encounters with other vehicles during the case.”

“It was very dangerous,” he said.

Frank Schwing, 57, a furloughed Commerce Department worker, said he was on the House side of the capitol when he saw police surround the black car.

“The sedan backed up and smashed into one of the cruisers, took off again around the south side of the Capitol,” Schwing said. “And that’s when I heard the gun shots. ”

A Capitol Police car could be seen with its bumper and front tires torn off and other damage.

Rep. Gerry Connolly, D-Mass., who was on the balcony talking to his colleagues, described a “burst” of gunfire from the House side of the Capitol, towards the House office buildings.

“It was like the first volley in a 21-gun salute,” Rep. Matthew Cartwright, D-Penn., told MNSNBC.

The FBI responded to the scene, and a helicopter landed in front of the Capitol to medevac the injured officer.

A message from the Capitol Police ordered anyone in a House office to “shelter in place,” but that order was lifted a short time later.

The House recessed, and the Senate went into a quorum call — dispensing momentarily with its official business — shortly thereafter.

“We’ve locked the doors. We closed the window shades. And we are awaiting further instructions,” Rep. Jared Polis, D-Colo., told MSNBC during the lockdown. “We’re more or less cut off here. We’re watching TV and just trying to figure out what happened.”

Though it was over quickly, nerves were still jangled.

“Shaken is a good word to describe how I’m feeling,” said Peter Plocki, a government worker furloughed during the shutdown who was on Capitol Hill to take a tour of the Supreme Court building and heard the shots.

The House reconvened at 3:30 p.m., and Rep. John Culberson, R-Texas, asked for a brief moment of silence in tribute to members of the Capitol Police injured in the incident. The House immediately pivoted back to debate over a small stopgap bill to reinstate funding for veterans’ affairs.

Congress has been locked for the past week and a half in a contentious debate over funding the government, a disagreement in which contributed to a government shutdown that began Monday.

Last night, Wisconsin Rep. Sean Duffy, R, was the victim of a “minor incident” outside of the Capitol complex.

“A random individual, unknown to the Congressman, began screaming at him and grabbed his arm,” a spokesperson for Duffy said in describing the incident. “Mr. Duffy was unharmed. He reported the incident in compliance with House security procedures. Congressman Duffy has requested no further action be taken and there will be no further comment on the matter at this time.”

On September 16, a deadly shooting occurred blocks south of the U.S. Capitol complex which contributed to a partial lockdown of the Capitol at that time.

A shooting on July 24, 1998 left two Capitol Police officers dead. And at a constituent event in her district in January 2011, then-Rep. Gabrielle Giffords, D-Ariz., was seriously injured and six others were killed in a shooting.

NBC News’ Jonathan Dienst and Andrew Rafferty contributed to this report.