Investigators are attempting to determine why an unarmed Stamford, Conn., woman ran her car into a security fence outside the White House on Thursday before leading authorities on a short chase that ended with her death in a hail of police gunfire near the U.S. Capitol.

 Miriam Carey, 34, was licensed as a dental hygienist in Connecticut and had recently been listed as an employee of a dentist there.

Rep. Mike McCaul, a Texas Republican and chairman of House Homeland Security Committee, who was briefed by FBI and Secret Service on the incident, said an 18-month-old girl was in car with Carey during the fatal confrontation. The child, who law enforcement sources said was believed to be Cary’s daughter, was not injured in the shooting and has been placed with child protective services, he said

McCaul said he was told by the briefers that the woman was unarmed and that investigators "think she had mental health issues."

A senior law enforcement official with direct knowledge of the case told NBC News that relatives interviewed by law enforcement officers tell them she suffered from a fall a couple of years ago and began to suffer mental issues.

Carey’s former employer, Connecticut dentist Barry Weiss, confirmed that she suffered a fall in January 2012 and was out for two to three weeks. When she returned, she was also pregnant, he said. 

He said he had fired Cary in August 2012 after numerous patients complained that she was rough.