Miriam Carey's 1-year-old daughter, who was in the vehicle during the deadly encounter with authorities, escaped serious injury and was taken into protective custody. The woman's family said she suffered from post-partum depression with psychosis.
Amy Carey-Jones, Miriam's other sister, said her sibling was a "law-abiding citizen, carefree and loving" while adding that she had been receiving medication and therapy.
A federal law enforcement official, who had been briefed about the investigation told the Associated Press that investigators were interviewing Carey's family about her mental state and examining writings found in her Stamford, Conn., condominium.
"We are seeing serious degradation in her mental health, certainly within the last 10 months, since December, ups and downs," the official said. "Our working theory is her mental health was a significant driver in her unexpected presence in D.C. yesterday."
Carey also believed President Barack Obama was communicating to her, the official said.
"Those communications were, of course, in her head," the official said, adding that concerns about her mental health were reported in the last year to Stamford police.
Dr. Brian Evans, a periodontist in Hamden, Conn., said Carey was fired from her job at his office about a year ago but wouldn't say why.
"Sometimes it just doesn't work out. There was nothing unusual about her leaving our office," Evans said.
He said Carey had been away from the job for a period after falling down a staircase and suffering a head injury and it was a few weeks after she returned to work that she was fired.
Carey was a licensed dental hygienist, according to records kept online by the state of Connecticut.