Authorities are investigating what led a woman with a toddler in her car to ram into a White House barrier and lead police on a high-speed chase to Capitol Hill.
The dramatic chase, which forced a brief lockdown of the Capitol and stirred panic among tourists, ended with the woman shot dead by police.
The driver was identified by law enforcement officials as Miriam Carey, of Stamford, Connecticut, it was widely reported in the US media.
The car chase forced a lockdown of the US CapitolShe was a 34-year-old dental hygienist and the mother of a young girl, the reports said.
Hours after the chase, the FBI and other agencies conducted a search of Carey's condominium building in Stamford.
ABC said Carey suffered from postnatal depression after the birth of her daughter.
The suspect was reportedly a dental hygienist. Pic: Facebook"She had post-partum depression after having the baby" last August, the woman's mother, Idella Carey, told ABC.
"A few months later, she got sick. She was depressed ... She was hospitalised."
The mother said Carey had "no history of violence" and she did not know why her daughter was in Washington, DC.
Other reports suggest that she had a history of mental health issues.
A federal law enforcement official told the Associated Press that Carey was delusional and believed President Barack Obama was communicating with her.
The official, who was briefed about the investigation, spoke on condition of anonymity because the person was not authorised to speak publicly about the ongoing probe.
The chase began shortly after 2pm on Thursday when a black Toyota Infiniti attempted to smash through a barricade close to the White House.
Video footage showed officers with guns drawn attempting to get the driver out of the vehicle.
But Carey spun the car around and sped away, knocking a law enforcement official.
The car raced up Pennsylvania Avenue toward the Capitol where Congress was in session.
A girl in the car was not hurtPolice chased and fired at the car, which came to a halt near the Capitol building, and she was shot dead.
By the end of the chase, two people were injured - a Secret Service member struck by the car outside the White House, and a Capitol Police officer whose vehicle hit a barricade during the chase.
A little girl who was in the suspect's car was not hurt. It was unclear if the child was the woman's daughter.
Officials said there appeared to be no direct link to terrorism and there was no indication that the woman was armed.
"This appears to be an isolated, singular matter," said Capitol Police Chief Kim Dine. "There is no nexus to terrorism."
Still, the high-speed chase rattled Washington two week after a gunman killed 12 people in a Navy Yard shooting.
Two law enforcement officials were injuredThe House and Senate, where politicians were debating how to end a government shutdown, abruptly suspended business.
Some politicians were told to shelter in place on the floor of the House. Outside, some tourists were frightened.
"I was just eating a hot dog over here and I heard about four or five gunshots, and then a swarm of police cars came in wailing their sirens," said Whit Dabney, a 13-year-old who was visiting Washington from Louisville, Kentucky.
People standing outside the Supreme Court across the street from Congress were hurried into the court building by authorities.
The White House was quickly locked down after the incident at Capitol Hill and the stretch of Pennsylvania Avenue in front of the compound was closed to pedestrians. Secret Service said the procedures were precautionary.
Police are trying to understand the motives behind Carey's gesture.
At her condo in Stamford, dozens of neighbours were forced to wait outside, as a bomb squad stood by.
Resident Eric Bredow, a banker, said police told him the suspect in the car chase was one of his neighbours.
"I see the door to my building open and the FBI bomb squad in front of it," he said.
Erin Jackson, 31, lived next door to Carey and said she doted on her young daughter, often taking the girl outside for picnics.
"She was pleasant. She was very happy with her daughter, very proud of her daughter," she said.
"I just never would have anticipated this in a million years."