What do you do if a elderly person becomes sick and does not have a POA?

my step grandfather become sick suddenly and my grandmother is deceased and he does not have a living will or a POA. My mom which is a step child has been paying his bills with cash that he had but she has no way of using his checking account, he has a daughter but she has nothing to do with him and my mom does not know what to do. As of now he will never be able to go home. He is on a ventilator and feeding tube.