This is the way the guys from Bowhuntingroad.com tell how this happened:
"Moose can be temperamental creatures that are easily started and quick to anger. Therefore, it is generally not recommended to approach one of these large animals unless it is sedated or you are a bear. Like most other mammals, moose cows are especially quick to resort to aggression when protecting their young, and as the motorists in the video below find out, can put quite the dent in a car. Chalk it up to another case of road rage:"