Person sold property that was mortgaged to bank twice

Sir/Madam,One person is threatening me with his influence in police. He is a fraud and he mortgaged his land and house their on, in a co operative bank after two year he sold the said property without bank clearance.this was done with the knowledge of the purchaser. the agreement was, purchaser will pay the balance loan. but purchaser didnt kept his promise. therefore he repurchased the said property. In 2010-11 again he mortgaged the said property in HDFC Bank by using new sale deeds, without clearing old encumbrance from district cooperative bank.In the year 2012 district co operative bank attached his property, and he went to debt control tribunal for relief. In the year 2014 he sold a portion of the said property to somebody there was an agent to manage the registration and other works, he paid 2 lacs commission. In 2015 he given police complaint that the said agent and his wife offered his son a job in titanium and cheated him. what can I do against him otherwise ? Thanking you