My son has been told hes going to die?

My son got blamed for something he didnt do and there were witnesess but each one is to terrified to give a statement, one of the attackers that beat my son got badly scarred with a bottle and now hes family are set for revenge.ive been told there a very bad family worse of the worse and been told dont press charges or it make it worse.they now coming round the house parking outside saying were gonna kill him, and i know they will.these arnt people that just all talk they actually carry out the attacks.im so worried police just said they keep eye out but he cant even go to college or out the house,were all prisoners in our own home, i know i can get someone that will make them go away for good but its a huge decision but i dont want my son to get hurt or killed,i dont know what to do.there a very bad family.