The United States Capitol was placed on lockdown Thursday afternoon after a woman tried to ram a car into the White House gate, was chased by Secret Service and exchanged shots with police, sources said. The suspect — who sources said had a child in the car — was shot and killed, and a shelter-in-place order was lifted at about 3 p.m. At least one Capitol Police officer was injured during the pursuit. President Barack Obama was briefed about the harrowing incident, which came in the midst of the government shutdown that has created a tense atmosphere on Capitol Hill. 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. Law-enforcement sources said she began firing and was shot. The child was reported to be safe.