Under the laws of most states in this country (California for example) the seller of a piece of property is required to disclose to all potential buyers all material facts affecting desirability or price paid before close of escrow of the unit.In California, one has to disclose in writing a death of a person on premises going three years back before the listing. Based upon what you have written, you seemingly have a violation of the law by the seller where your recourse could be the cancellation of the purchase. I suggest that you consult with a real estate attorney for assistance.