You would have to bring a legal action to have a court declare him incompetent (based on medical evidence--e.g. the tesimony of and reports from physicians who have examined or treated him)  to manage his own affairs and have someone (you) appointed his legal guardian to manage his affairs for him. This action would be brought in family court. I can be brought on an expedited ("emergent") basis to get it done more quickly than legal actions generally take. This would be a *very* complicated action for a layperson (non-lawyer) to bring and then prove (i.e. obtain, marshal, and present the evidence of incompetency); if you want to explore this option, consult with an elder law attorney, who can help you bring the action.  Until he is declared incompetent, he can continue to give away his money or take other unfortunate actions: do not delay in acting.