Getting threats from my relatives to press false charges on me

One of my relative (my father's brother) came to my home today (13/4/18) after 4-5 years and has threatened to charge me with murder case of my father when in fact my father went missing 4 years ago. My father had lost his speech and his memory at that time due to some neuro problems. I searched for my father in all places I can but I couldn't find him. This said relative has harassed my husband and me. He tried to physically harm us and also used abusive language to us. I don't know what to do if this person falsely press charges on me. Pls help... He says that he'll complain telling that I and my sick mother killed my dear father. We're not over the emotional distress on acc of my father going missing on top of that my relatives keep harassing us in front of all neighbors using abusive language and telling that we killed our dear father. How can you save me and my family from this harassment. also kindly let me know if I'll have to go through hardship on account of this false charge?