My 8 Year Old Has Started Biting People At School.

My 8 year old has started biting people at school. The first time we thought it may have been justified as he was being pinched and told the kid to get off of him. Today, he bit another kid at school and has been suspended. He lost his mother 4years ago in a major car wreck that almost took his life as well. He has never done anything like this before. He is always a happy go lucky child and gets along with anyone and everyone. I'm at a loss on what is going on. I'm worried something serious is going on and he is afraid to talk to me (step mother) or his father.