Transcript for Miriam Carey's Medical History and the High-Speed Police Chase on Capitol Hill
The young mother with her baby in her car who triggered 38 minutes of chaos at the capitol. Miriam carey shot dead after a high-speed chase with police. Her baby girl is all right. Tonight we learn more about her mental state. Family and friends speaking out. And correspondent pierre thomas is reporting. Reporter: We now know that miriam carey was the woman behind the wheel, toddler in tow who led police on a high speed chase. This man saw her tuesday. Everything was okay. She went about her business. It's just -- Reporter: Abc news learned carey had a history of mental illness, appeared to intensify after her baby was born in august 2012. It was then her mother tells abc news, she was diagnosed with post partum depression. In december, according to a stamford, connecticut police report, a man described as carey's boyfriend called in expressing concern for the safety of their daughter. Then five months old. He said carey was delusional, emotionally disturbed. The boyfriend claimed carey believed she was a prophet, whose home was under 24 hour surveillance by president obama and national tv networks. She was taken to the hospital at least two other times that month. A report by connecticut authorities describes her as on medication for unknown mental illness. With a family history of schizophrenia. She seemed to stabilize, but something went terribly wrong. And by yesterday, carey was battling police, who killed her firing more than a dozen shots. She was apparently unarmed. But police believed she was a threat. What were police thinking at that moment? They are thinking, she's about to use this car as a lethal weapon. And so that justifies deadly force to shoot at her. Reporter: Police are searching through carey's computers looking for any clue to point toward motive. Tonight law enforcement tells me they may never discover a sane answer as to why this happened. David. Pierre tom this our washington bureau. Pierre, thank you.
This transcript has been automatically generated and may not be 100% accurate.