Good Samaritan car damage – who is responsible?

A friend of mine saw a man whose car was stuck in a snow bank, he stopped and offered to help push it out. He agreed. Some other people stopped and joined in. Someone pushed in the wing of the car and it broke. The driver was furious and demanded compensation, which has not happened so far. My friend thinks that the driver said the person pushing the spoiler, but of course one can doubt that (he told this purpose, if necessary). They are good Samaritans who are trying to help those responsible for the damage? If you …