A week in which Washington was first shaken by a shutdown of the federal government and then rattled by a car chase and shooting on Capitol Hill ended with scenes of a medical helicopter evacuating a man who was on fire in the National Mall.
A witness described seeing the man pour a red can of petrol on his head and then set himself on fire.
Nicole Didyk said she saw four or five men with their shirts off, using the clothing to beat out flames that were engulfing a man's body. The men putting out the fire were passers-by, she said, and one of them told her that the man had ''saluted the Capitol and then lit himself on fire''.
Out and about: Despite security scares, Barack Obama surprises bystanders on Friday with a rare stroll to grab lunch at a sandwich shop a block from the White House. Photo: AFP
One of the men putting out the flames told Ms Didyk that the man said ''thank you'' after the men put out the flames.
Meghan Van Heertum, an emergency room nurse visiting Washington from Wisconsin, said she saw a group of people huddled trying to put out a fire. ''I smelled burnt flesh and put two and two together,'' she said.
Meanwhile, questions are being raised over the police response to the car chase that ended with a 34-year-old mother being shot dead in front of her one-year-old daughter.
Later that day, people rush to help a man who apparently set fire to himself in the National Mall. Photo: AP/Katy Scheflen
Miriam Carey, a dental hygienist, allegedly rammed a barrier at the White House in a black Infiniti two-door coupe, then sped down Pennsylvania Avenue with her baby girl at her side.
On Facebook, there was an outpouring of anger directed at police on a memorial page for Carey created by a friend in the wake of the incident.
''I hope her family sues the Capitol Police Dept,'' wrote one woman, referring to the well-armed specialised force that patrols the Capitol building and its surroundings.
''Why couldn't they shoot the tyres of the vehicle? Deadly force with a child in the car? I just can't understand this.''
The infant was placed in protective custody in a Washington children's hospital after the drama.
Police who searched Ms Carey's home found a crib, children's toys and baby bottles, but no weapons or anti-government material, the Hartford Courant newspaper reported.
Carey's mother Idella Carey told ABC News that her daughter had ''no history of violence'' and that it was a mystery why she was in the nation's capital in the first place.
''She had post-partum depression after having the baby'' in August last year, she said. ''A few months later, she got sick. She was depressed … She was hospitalised.''
Quoting anonymous police sources, NBC News said Carey had ''a history of mental issues'' and that investigators had ''discovered indications'' that she believed she was being stalked by President Barack Obama.
Officials said the chase began at the outer perimeter of the White House security cordon, where the suspect's car struck a barrier and a uniformed Secret Service officer.
No shots were fired initially, but agents gave chase as the car sped away.
As the vehicle closed in on the Capitol, the seat of Congress, it was cornered by police vehicles and armed officers on foot.
Footage aired by TV broadcasters showed the car executing a tight U-turn as shots rang out, and then speeding off.
Shortly afterwards it hit another barrier and more shots were fired.