BOSTON — Authorities believe a mother killed her two young children and then herself in Boston on Christmas Day.

Erin Pascal, 40, and her children, Allison, 4, and Andrew, 15 months, were found on the sidewalk outside a parking garage on Wednesday afternoon and rushed to a hospital where they were pronounced dead.

It’s still not clear exactly how the children died, but Suffolk District Attorney Rachael Rollins told reporters Thursday that investigators believe the two children fell from the garage’s roof first, followed by Pascal.

“All things are indicating” the deaths were a “double murder-suicide,” Rollins said.

“Yesterday the unspeakable happened and now we are all struggling to make sense of the circumstances surrounding these deaths,” she said.

Rollins said the father of the children was notified Wednesday of their deaths and that officials are still reviewing surveillance video.

They’re also searching for clues in the Boston family’s vehicle, which was parked at the top level of the garage, which is adjacent to the Ruggles MBTA rail station, she said.

This undated photograph shows Erin Pascal of the West Roxbury neighborhood of Boston. Authorities believe Pascal killed her two young children and then herself in Boston on Christmas Day. The family was found on the sidewalk outside a parking garage on Wednesday afternoon. Suffolk County District Attorney’s office via Associated Press

“For a parent to come to a place in which they harm their children in this way, indicates that their mental health struggles were severe and in need of immediate supports,” she said.

Five people have now died in recent months at the garage, which is owned by Northeastern University, Rollins said.

Northeastern University said it has indefinitely blocked pedestrian and vehicular access to the top two floors of the garage in response to the latest deaths.