I feel unsafe living with my brother

I was sitting downstairs minding my own business talking to my brother when he turns around and sneezes (basically spraying saliva and mucus all over me) on purpose. We start arguing about the fact that it is weird and discusting to do that. I went upstairs but he followed me unsatisfied with the argument he tries to tell me we are going to go downstairs and fight. I am 15 and he is 17 I dont want to fight him and he tells me dont tell our mother and father who are sleeping in their rooms. He backs me into a corner in my room and says come downstairs to fight him as to not alert our parents. I say no and he starts throwing a psychotic fit in my room tearing my decorations off the wall and throwing them on the floor than he goes to his room and slams the door. I have told my mother and she says she will punish him in the morning. I dont know what to do i dont feel safe in my own home to leave my room. The only reason he didnt attack me is because our parents couldnt here us upstairs and i refused to go downstairs. As it is the summer when our parents work we are home alone. I dont feel comfortable and worry for my own wellbeing in that condition. We have had one serious fight in the last 1-2 years which he had started out aggressing and ending up with minor injuries on both of our ends.