Individual forced to give blank cheques, how to recuperate


My father owed someone money. This guy came to my home when my father was not present and threatened my mother and took blank cheques from her. My father later filed harassment in police station and form then on the person did not harass. This happened in 2014. My father died last year, now the person is harassing my mother again. What should we do?

ps: The person already encashed one cheque at that time and had told that he will not bother again, no written proof available for this.