BOSTON >> Authorities believe a mother killed herself after her two young children fell from the roof of a Boston parking garage on Christmas Day and died.

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. All three were pronounced dead at a hospital Wednesday. It’s still not clear exactly how the children died.

“Our investigation is showing the two children fell first, and then the parent after,” Rollins told WBUR radio on Thursday. She said that “all things are indicating” the mother died by suicide.

Rollins said the father of the children was notified Wednesday of their deaths. More details were expected to be released Thursday afternoon.

News footage showed police on Wednesday looking at an SUV, with several doors wide open, parked on the top level of the parking garage, which is adjacent to the Ruggles MBTA rail station. Boston Police Commissioner William Gross said there were two child car seats in the vehicle.

“Today is a tragedy,” he said Wednesday, declining to speculate on what happened.

The deaths occurred outside a garage that is owned by Northeastern University. The Boston Globe reports it’s the same garage where a Boston College student killed himself earlier this year.

“As a mother, it was incredibly hard, this scene in particular, where there were two young children that lost their lives today,” Rollins said Wednesday. “We’re going to do everything that we can to get the answers.”