sadist in my apartment what to do?

hello Sir/madam..I live in a rented apartment in first floor.there is a sadistic fellow in second floor he is also rented.he daily beats his wife and he suspects illegal affair of his wife with me.i am a merit student and preparing for competitive exams.And I talked with his father in law about his character...and he told he also suffered a lot...once his daughter tried to commit suicide with his behaviour he said...and all family members of that sadist had left him.even his friends left him.And this guy (sadist)to cover his mistakes he joined PRESS.Recently without I doing anything to him.he lodged a complaint against me that he has threat from me.And my father who knows everything about him lodged reverse complaint against him that we had threat.The SI didn't file FIR but took signature from both of us on white paper and said both of u don't quarrel.Now I'm taking coaching classes out of state.He has two children 2nd,6th class,if anything happens to them will i be responsible?? and any affect to my career.he is sadist he wants to spoil my study life ..in always. he will tear his shirt and go to police station that bet him that kind of sadist what to do...he feared his wife I she tells about his sadist nature to anyone he will leave two children abandoned.Suggest me some help unable to concentrate on studies...