This is something we really can't comment on here.
One because there a myriad of reason why people get angry. Sometimes it may be fear of the unknown, fear of losing something or that we have a perception of being treated unfairly. However, anger can arise from many other hidden factors and we can't possibly know the answer to your question. Perhaps A school counselor or trusted teacher could help you resolve your issue with the dean.
Two it may well be a medical issue meaning you should seek help from your doctor immediately.
In any event, it is clearly worrying you so you should find a qualified doctor or counselor to help you parse the situation to see what is actually causing the anger.
As there is nothing more to say here. I am closing this thread.