Threat calls related to civil cases pending in the court

My father is a Licensee of a C.S and F.L shop. One of his ex-Salesman has wrongly filed a Money Suit and a Title Suit on him which is pending in the Court of Law. Today we received a threat call against the same from the ex-Salesmans nephew, where they wanted us to sell the licence to them as well as a lot of verbal abuse and also challenging us to do whatever we can and report them wherever we can. We have the same recorded in our phone. We have lodged a complaint about the same with the local police, and the police has asked us to include the copy of the complaint with our cases. My parents are Senior Citizens and I am really worried about their welfare as the call even included statements like they could have finished us off but they didn't and so on. I really want to know what can be the next step to this.