The Hampden County DA says they know what happened at a Berkshire Avenie home this week. The just don't know why.
D-A Anthony Gulluni says 34-year-old Victor Nieves opened fire on a family Monday afternoon.
Police say he killed a 52-year-old woman and the family dog, and then shot and injured two of the three children in the house before fatally shooting himself.
Police say a ten-year-old child is in critical condition at a Boston Hospital.
A 12-year-old is in stable condition in a Springfield hospital while a third child, a five-year-old was not physically harmed.
The DA says Nieves lived in the upstairs apartment of the multi family home and forcibly entered one of the apartments and opened fire.
The woman killed was the grandmother of the three children.
The investigation is continuing.
Investigators say they are still seeking a motive for the tragedy.
(Photo provided by Hampden County DA Office)