We both a house months before the market co-lapse?

in our son name, Loan is FHA the house is been empty for three years, the value declined for 160,000 that we paid to provably,80,000 we are loosing money from our retire to paid a mortgage that don't have any value, me and my husband are the co-signer and our son finish buying another house, I want to know is we return this house to the bank, they can take our properties and money, advise me what to do please