Children bite in order to cope with a challenge or fulfill a need.  For example, he may be biting to express a strong feeling (like frustration), to communicate a need for personal space (maybe another child is standing too close) or to satisfy a need for oral stimulation (maybe he is teething or even hungry).  Trying your best to understand the underlying cause of the biting will help you develop an effective response.  Giving a child the words he does not yet have is always helpful- you can communicate what he cannot say.  This shows that you understand how he feels, and shows him an appropriate way to interact.  You seem frustrated right now.  Do you need some help?   Susie is in your way, you can tell her “excuse me.”