Carey's mother, Idella Carey, told ABC News on Thursday night that her daughter began suffering from postpartum depression after giving birth to her daughter, Erica, in August 2012.
"A few months later, she got sick," she said. "She was depressed. ... She was hospitalized."
Idella Carey said her daughter had "no history of violence," and she didn't know why she was in Washington on Thursday. She said she thought Carey was taking Erica to a doctor's appointment in Connecticut.
Connecticut records show Carey had been a licensed dental hygienist since 2009. Records show the license expired on Thursday.
Dr. Brian Evans, a periodontist in Hamden, Conn., said Carey worked as a hygienist in his office for about two years before she was fired a year ago. He would not go into detail about the reasons surrounding her departure.
"Sometimes it just doesn't work out. There was nothing unusual about her leaving our office," he said.
He said Carey had been away from the job for a period after falling down a staircase and suffering a head injury, and she learned she was pregnant during the time she was hospitalized. He said it was a few weeks after she returned to the office that she was fired.
"We're shocked to know this happened and we feel saddened for her family and all those involved," he said.
Police said there appeared to be no direct link to terrorism, and there was no indication the woman was even armed. Capitol Police Chief Kim Dine, whose officers have been working without pay as a result of the shutdown, called it an "isolated, singular matter."
Still, tourists, congressional staff and even some senators watched anxiously as a caravan of law enforcement vehicles chased a black Infiniti with Connecticut license plates down Constitution Avenue outside the Capitol and as officers with high-powered firearms canvassed the area. The House and Senate both abruptly suspended business, a lawmaker's speech cut off in mid-sentence, as the Capitol Police broadcast a message over its emergency radio system telling people to stay in place and move away from the windows.
The woman's car at one point had been surrounded by police cars and she managed to escape, careening around a traffic circle and past the north side of the Capitol. Video shot by a TV cameraman showed police pointing firearms at her car before she rammed a Secret Service vehicle and continued driving. Metropolitan Police Chief Cathy Lanier said police shot and killed her a block northeast of the historic building.
In Stamford, the FBI served a search warrant in connection with the investigation and police cordoned off a condominium building and the surrounding neighborhood in the shoreline city.
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."
Jackson said Carey was upset earlier this summer when the tires were stolen off her car, but she said her neighbor seemed content. She said she never heard her say anything political.