In a statement, Mayor Martin J. Walsh said, "This is a disgusting tragedy for this family on this Christmas Day".
When they arrived, they found Erin Pascal and her two children unconscious on the sidewalk.
There have been no suicide notes found and no known complaints about the mother, Rollins said.
"There were children's shoes and an adult shoe".
"We want everyone to know ... we will do everything in our power to find out everything we can about this death investigation", Gross said.
Suffolk District Attorney Rachael Rollins said Thursday the woman, whom she did not identify, was 40 years old, and her children were 15 months and 4 years old.
Investigators are looking into reports that a 911 call was placed shortly before the incident on Wednesday.
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Ralph Northam, a Democrat, tweeted Sunday afternoon, thanking emergency crews, first responders and hospital staffers. Detours were set up with the help of the York County Sheriff's office and Virginia's Department of Transportation.
Christmas Day marked a disgusting tragedy that claimed the lives of two children under the age of 5 and their mother, who is suspected in their deaths.
Investigators are still searching Pascal's black SUV - which was left parked on the rooftop with three of its doors open - as well as her phone and any surveillance footage, Rollins said.
"It's a tragedy", Boston Police Commissioner William Gross told reporters Wednesday. There was the impact of the fall, was visible from the street. "And if it'd happened on any day, it would be a tragedy, but it happened on Christmas Day, which - whether you celebrate that holiday or not - this is a sacred season in many cultures, and just to see a family - where many of us were home, I hope, celebrating and loving ours - that this family ended on that day, or the vast majority of them did".
Shortly after the event took place, Northeastern University sent an alert signal of police action near the Ruggles MBTA Station. "Please utilize this help". A Boston College student killed himself by jumping off the top of the garage earlier this year. His girlfriend, Inyoung You, is being charged with involuntary manslaughter.
Northeastern University spokeswoman Shannon Nargi said the university is addressing security.
The university, in response to the incident on Christmas Day, "has indefinitely blocked both pedestrian and vehicular access to the top two floors of the Renaissance Park garage". "This restricted access will continue until a permanent solution is implemented", Nargi said. The International Association for Suicide Prevention and Befrienders Worldwide also can provide contact information for crisis centers around the world.