Tampa, Florida -- More details are emerging about the bizarre behavior of this mother shot to death after investigators say she tired to drive through a barricade near the White House and the Capitol.

Family members of 34-year-old Miriam Carey say she thought the President was talking to herand even stalking her.

Friday, a day afterinvestigators say Careyrammed White House barricades and then led police on a chase thatset in motion the lockdown of the U.S. Capitol, detectives are still trying to learn more about what may have set Carey off.

According to a law enforcement source, Carey's boyfriend contacted police back in Decembersaying he was worriedfor their child's safety and that she was suffering from postpartum depression. Carey's mother also says her daughter was suffering from it.

SEE ALSO:Mother of woman killed in DC chase was depressed

Still, the incidentcaught most of Carey'sfamily, friends and co-workers by surprise because they say she never acted out.

10 Newsspoke with Dr. George Northrup, of Tampa, about it. He's been a general and forensic psychiatrist for the past decade and says,"The fact that there's no history of violence -- that's really the leading question. It's when there's either behavioral changes or they're on the phone and they're saying things that don't make sense -- that's when you have to do something."

Investigators searched Carey's Stamford, Connecticut apartment where they found two medications. One of the prescriptions was an anti-depressant. The other was a drug that's used to treat conditions such asbipolar disorder orschizophrenia.

Dr. Northrup says postpartum problems are prevalent.

"Many women suffer from a case of the baby blues which is a short period of sadness. Sometimes that will continue into postpartum depression and in much rarer cases postpartum psychosis -- but postpartum psychosis can most times result in a more tragic outcome."

Northrupsays counseling and medication can help.

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