Motive mystery over woman killed in US Capitol drama

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 year-old baby girl at her side.

The infant was placed in protective custody in a Washington children's hospital in the aftermath of a drama that triggered a lockdown of the Capitol on day three of a US government shutdown.

Police who searched her home in Stamford, Connecticut 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 hospitalized."

Several US news media Friday quoted a law enforcement source who they did not name as saying that Carey had had delusional thoughts that President Barack Obama was communicating with her and that she was under electronic surveillance.

CBS News said Carey had sustained a head injury in a fall in April 2012 for which she got hospital treatment. It also said she had been fired from her job at a dental clinic after an argument over a handicapped parking spot.

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 specialized force that patrols the Capitol building and its surroundings.

"Why couldn't they shoot the tires of the vehicle? Deadly force with a child in the car? I just can't understand this."

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 afterward it hit another barrier and more shots were fired.

It was the second major security breach in the US capital in less than three weeks. On September 16, a deranged gunman stormed the nearby Navy Yard and killed 12 people.

In Stamford, an hour's drive from New York City, on Thursday local police and FBI agents sealed off the residential complex housing Carey's $242,000 condo and began an overnight search for clues.

"A full investigation is under way by federal authorities who are in Stamford currently," said Stamford mayor Michael Pavia, quoted by the city's Advocate newspaper.

"Stamford police are assisting ... as needed."

US news media, citing public records, said Carey, an African-American, lived near her family in the New York borough of Brooklyn for several years prior to moving to Stamford in 2002.

A college graduate and registered dental assistant, she worked at Advanced Periodontics in Hamden, Connecticut, which in 2011 published a newsletter -- still on its website Friday -- raving about her people skills.

"We are excited to have Miriam!" it said.

"She not only brings a delightful bedside manner, but also has a degree in nutrition that we hope to utilize in educating our patients about how important their diet is to maintaining optimum oral health."

"I would never in a million years believe that she would do something like this," periodontist Steven Oken, for whom Carey once worked, told ABC News.