How do I sue a bank over a reverse mortgage?

the bank let my Dad have a reverse mortgage when he was already diagnosed with dementia for approx $250,000. my brother went with him to 'help' him. my brother has been indicted by a grand jury for elder abuse and elder fiduciary abuse for using a good deal of the money for personal use and none for Dad. now I want to go after the bank. I do not know how to go about locating an attorney for this but have heard there are some that will do this on contingency. This bank has stopped giving reverse mortgages due to the high volume of law suits for this very same issue.