Since the bank does not have exclusive ownership at the present time you would have to deal with the present owner. Your best alternative is to wait until the bank takes ownership, monitor the local MLS, and be ready to act on it as soon as it comes onto the market.
Banks do not deal directly with the sale of real estate and will place it in the hands of real estate professionals at some point after taking possession.
You can attend the sheriff's sale and bid on the property there. This can be risky because of the fact that the liens and judgements on the subject property become your responsibility upon purchase and will need to be satisfied by you. This is why most of these properties end up back in the hands of the lender.