My foster brother is getting bullied, badly!?!?

One day he ran in crying and he is 12, then I went up to ask him what is wrong and he told me to F*** off. The Next day he came in not crying, but stomping up the stairs, LOUDLY. I asked him again then he told me. He is from Africa and is obviously, how will i say it.. Colored? But in other words Black.. He said about 16 and 17 year old boys are bullying him for his skin color. I forgot to mention he came in with all his clothes very wet, and said that was because they pushed him into our River in our town which is actual very horrible:S it has lots of rubbish, believe it or not bones.. and dead fish. Also he mentioned that they grabbed him by his collar and said "If you don't go back to your stupid and gay country or f***ing continent we will stab you in the neck." I have got bullied too but not this bad. He hides in his wardrobe in the morning so my mom and dad won't send him to school. Then about 2 days later they came to our door and said can we see Derek and then my mom said No and closed the door then they actually smashed the window with a rock and ran away. If you read all of this, PLEASE tell me how my brother can be happy again?