"We're still very confused as a family why she's not still alive," Amy Carey-Jones said late Friday, speaking of her 34-year-old sister, Miriam Carey. "I really feel like it's not justified, not justified."
Another sister, retired New York City police officer Valarie Carey, said there was "no need for a gun to be used when there was no gunfire coming from the vehicle."
The sisters spoke outside Valarie Carey's home in Brooklyn Friday night after traveling to Washington to identify Miriam Carey's body.
Carey-Jones said her sister had been on medication for postpartum depression but was being taken off the drugs under medical supervision.
"They told her she could get off medication," Carey-Jones said, adding, "There were no indications she was unstable."
Meanwhile the investigation continues into why the Stamford, Connecticut woman tried to breach a White House barrier, setting off a high-speed car chase and ended with her being killed by police.
Also Friday night the New York based Law Enforcement Alliance demanded answers about why Capitol Police felt there was no other way to stop her car.
"Twice this vehicle was stopped and twice surrounded, and they still fired at it," said Darrin Green, of the Law Enforcement Alliance.
And new details are emerging about 34-year-old Miriam Carey's debilitating mental state and increasingly erratic behavior.
The suspect's mother, Idella Carey, says her daughter was suffering from post-partum depression and had a history of mental illness. Miriam Carey's alleged actions put Capitol Hill on lockdown Thursday and left a city still rattled from the Navy Yard shooting on edge.
Carey lived in Stamford, where police waited hours to get the warrant needed to finally break into her apartment Thursday night.
About 50 of her neighbors were evacuated from their apartments and the street was closed off while bomb squad and hazardous materials units moved in.
"It's a joint operation," Stamford police chief John Fontneau said. "We're working the FBI, Secret Service, state police, Stamford Police Department bomb team and state of Connecticut."
The law enforcement activity at the scene ended Friday morning, with authorities saying the building was secured as of 7 a.m. The only apparent piece of evidence that police removed was a computer. Residents were then allowed to return.
Family members say Carey's history of mental illness and troubles with post-partum depression grew so severe that the young mother had to be hospitalized at one point.
Sources tell ABC News that the father of Carey's 1-year-old daughter, Erica Frances, told police months ago that she had begun to show signs of mental illness around September of 2012. Police were called to her home on several different occasions after that.
According to the sources, on morning of December 10, Stamford police responded to a suspected child abuse and neglect issue reported by the 54-year-old then-boyfriend. When police arrived, the boyfriend told them that Carey was emotionally disturbed.
He said he was afraid for his daughter's safety, and Carey was not speaking rationally. He said she was delusional and believed she was the prophet of Stamford who was in contact with President Obama. She also said that Obama had placed the city of Stamford under lockdown and had placed her residence under electronic surveillance, which was being fed live to all national news outlets.
Officers offered to assist Carey with the baby, but she said that they would have to tackle her on live television in order to take her to the Stamford Hospital. Officers then forcibly took the baby and handcuffed Carey, but she managed to slip out of one of the cuffs. After a brief struggle, she was re-cuffed and transported for a mental health evaluation.
As a result, Carey was prescribed Ambien because she complained of trouble sleeping.
Then, on December 21, the boyfriend reported to police that Carey had driven to Brooklyn with Erica the night before to attend a family party and had yet to return. Upon their return later that morning, the boyfriend reported Miriam was off of her medications and tried to fight him.
Police were again called to the residence, where Carey became combative, injuring an officer, before being transported to Stamford Hospital. Internal reports at the time said Carey was on medication for unknown mental illness and has a family history of schizophrenia.
During a follow up visit to hospital in late December, the boyfriend told a social worker that Carey suffered from post-partum depression, and he was concerned she was not eating well.
The social worker contacted the family on January 6, and the boyfriend said that Miriam was doing fantastic and was 100 percent back to normal. Days later, Carey told the social worker that prior to her initial hospitalization, she had felt restless, tired, delusional and had difficulty sleeping. She told the social worker that doctors at Stamford Hospital confirmed she had post-partum depression after her initial hospitalization; however, she did not want to disclose the medication she was prescribed. Miriam also told the social worker that she was receiving treatment at a mental health facility.
Carey, a dental hygienist, bought a condo in the Woodside Green Complex in 2009 for $242,000.
The complex filed suit against Carey last year, but the suit was withdrawn a couple of months later.
She worked for a dental practice in Hamden, but her name no longer appears on the practice's website directory.
Carey reportedly had started a home-based business called Experienced Dental Placements, which appeared to operate as a temporary employment firm.
Carey grew up in Bedford-Stuyvesant, Brooklyn, and police went to her childhood home to question her family in an effort to figure out exactly what happened.
Her relatives had been huddled inside the Marion Street home of sister Valarie Carey, a former NYPD sergeant who retired in 2006 after about 12 years on the force, trying to come to grips with the tragic occurrence in DC. They left the house early Friday morning without talking, but are expected to comment Friday evening.
No motive has been identified, and no one who knew her could explain the actions of a woman who seemed to be on the right track.
"They're like any other family, you know?" family attorney Eric Sanders said. "They're disturbed about these different things. But we have to mend the family first and then find out what happened down in DC."
Friends also expressed concern for Carey's 1-year-old daughter, Erica, who is now motherless.
"I grew up with her, and it doesn't seem like she would go through something like that," friend Donald Knowles said. "It's just shocking."
Idella Carey said her daughter had "no history of violence," and she didn't know why she was in Washington, D.C., on Thursday. She said she thought Carey was taking Erica to a doctor's appointment in Connecticut.
Carey's boss, Dr. Steven Oken, described Carey as a person who was "always happy."
"I would never in a million years believe that she would do something like this," he said. "It's the furthest thing from anything I would think she would do, especially with her child in the car. I am floored that it would be her."
The investigation is ongoing.