My father committed suicide , do to frequent visit of group of people related to promissory note

My father being as a mediator between two persons related to money transaction In April , my father Diagnosis Cancer in body . After getting known this information . Money lenders forced my father to write new promissory note because you are mediator related to amount Given to ex party. ( I am working in another city , so I don't know any thing about this matter ) My father severely struggling on bed do to health issue. On that time , lender bring many people into the house surrounding my father who is alone on bed , forced to get signature. After two days my father committed suicide drinking poision. After completion of all my father rituals , again that person along with group of people asking me to settle . I met local police , to enquire about my father cause of death , please punish related person. But police said " you have to inform us immediately on your father's expire. Now it's not possible almost 15 days have completed. I came back with empty hands Now those lenders send legal notice to me and my brother Related to promissory note. I didn't take any thing from my father. My younger brother got agriculture land from my father. My father got that agriculture land from my grandfather. What is my situation and my brother situation.