By Chelsea J. Carter
(CNN) -- Amy Carey-Jones heard the news from someone, but she refused to believe it.
It couldn't be her sister who authorities say rammed a barricade at the White House and then led police on a high-velocity chase through the heart of the nation's capital, ending with gunshots that left the woman dead.
No, not her sister, she said. Then she turned on the television to the images of a smashed car and police.
"I just saw the same clip over and over," Carey-Jones said Friday on CNN's AC360. "I did recognize the car. It just didn't seem real."
A day after Miriam Carey led police on the chase with her 1-year-old daughter in the back seat, authorities are searching for clues to explain the bizarre chain of events that led to her death.
So, too, is her family.
"We are still trying to put the pieces together," Carey-Jones said.
Neither she nor her other sister, Valarie Carey, know why Miriam Carey was in Washington, D.C. on Thursday.
"We will never know what Mariam was thinking in those last hours before she died, and we can only speculate. Our real concern is why (this happened) and were things done properly? Was there some other way she could have been helped so that it didn't end tragically?"
Washington Metropolitan Police Chief Cathy Lanier said that officers of the U.S. Capitol Police and Secret Service acted within commonly accepted use-of-force policies and practices in reaction to an intentional series of violent acts.
Although Miriam Carey was shot while driving with her baby girl, the child was uninjured. The Carey family told CNN they have been told the girl is safe.
"We don't know exactly where she is," said Valarie Carey.
The girl has been taken into protective custody by the D.C. Child and Family Services Agency. She has been temporarily placed with a foster family, according an agency spokesperson, who declined to be identified.
Miriam Carey's boyfriend reportedly told police last winter that she appeared to be delusional. The boyfriend said she claimed President Barack Obama had placed Stamford, Connecticut, where she lived, under lockdown and that her house was under electronic surveillance, said a law enforcement source familiar with the investigation. The source, who spoke on condition of anonymity, was not authorized to release details to the media.
Reports have surfaced following the deadly incident that Miriam Carey was being treated for schizophrenia and bipolar disorder, claims the Carey family vehemently denied.
A few months after her daughter was born, Miriam Carey was diagnosed with postpartum depression with psychosis, the sisters said.
Postpartum psychosis can cause delusions and paranoia, according to medical experts.
"There wasn't a pattern. It was something that occurred suddenly," Carey-Jones said. "She seemed overwhelmed. There was a lot of stress.
"There was not moments of her walking around with delusions. That was not what was going on."
But her sister was making progress with the help of counseling and medications.
Carey-Jones said her sister recently told her that the doctors told her she didn't need the medication anymore.
"They tapered her off the medications, and she said she felt fine," Carey-Jones said.
The sisters declined to discuss what medication Miriam Carey had taken.
Despite reported claims by Miriam Carey's boyfriend that she had been delusional, the Carey sisters say they saw no signs of any problems. Authorities have not officially linked the incident to mental illness or any other factor.
"She has never disclosed anything of that nature, and since my sister is not here to speak for herself that statement in and of itself is very questionable," Valarie Carey said.
To the Careys, their sister was a "vibrant" woman who had everything to live for -- especially her 1-year-old daughter.
Miriam Carey, they said, wanted to teach.
"She always talked about teaching. Her field was dental hygienist, and she wanted to go further and give back in the field," Carey-Jones said.
The sisters are struggling to reconcile the woman they know -- loving sister, mother and friend -- with the one who authorities say was behind the deadly chase.
"When you see the information reported, it doesn't add up," Carey-Jones said.
The family is questioning whether shooting Miriam Carey was the only way to end the chase.
"We want to know if protocols were followed," family attorney Eric Sanders said on AC360.
"We are interested in finding out what happened. ...We are going to conduct our investigation, and we are not going to go with just what the government said."
Authorities have acknowledged no shots were fired from Carey's black Infiniti as it raced through the streets.
"My sister just totally didn't deserve this," said Valarie Carey, who was a New York police officer. "There are going to be a lot of different stories being told by people that claim they may know her. They don't. She was a law-abiding citizen. She had no political agenda."