How to stop my brother from embarrising my family?

my brother is 6 years old. whenever we go to the store he whiles and complains for what he wants.when my parents say no he goes into a tantrum and screams and kicks and cries. everyone close by give a strange look and I want to kill myself. he also cries when he doesnt win and it annoys everyone. Is there a punishment for his behavior? because all my parents do is yell at him and he starts screaming back and running around the house and hitting his head on the wall. I need help because im on the breaking point and I want to punch or slap him so badly!