My Great-grandmother Appointed Me As Poa, But Her Son Is Being A Hindrance.

My great-grandmother is currently in a long-term hospital. She has elected to be intubated and is scheduled to go under tomorrow. After she expressed her wishes to the doctors and caseworker, she specifically appointed me as her POA. She signed both a medical and durable POA, which entails access to finances.

For context, I have been doing all of the legwork with her care. Prior to her being transferred to the facility where she's currently located, she experienced inadequate care that required HOURS of me making phone calls to advocacy groups, updating relatives non-stop, and threatening people's medical licenses until she finally got competent care. Her son, my great-uncle, has done nothing. He lives out-of-state and comes and goes. I understand that he has a life and job, but when he is in town to see her, he has taken zero part in advocating for her, and actually tried to put her in hospice (there are assets that probably will go to him so I suspect he's just trying to "get it over with").

Prior to her appointing me as POA, he came by her house and took her purse that had all of her bank cards. From my understanding, he may be an authorized user on some of them. I have asked for them back because I am now in charge of my great-grandmother's finances, but he has not responded. My great-grandmother can no longer speak, so her calling him to demand it is no-go. I don't even know who she banks with for me to call and ensure he hasn't been running amuck with her money. Can I get law enforcement involved? This is super time sensitive, so I don't know if legal intervention can take place soon enough.

I would GREATLY appreciate input from anyone with any family law knowledge, specifically POA. Thank you!

Side note: she gets intubated tomorrow, and after throwing a fit this morning at the hospital when he found out about the POA, he left and hasn't been back. I assume he's spent the day trying to find an attorney willing to try to intervene and nullify the POA. Rather than spend the day with his mother the last day she's coherent (and may not ever be again), he wants to fight against her wishes. It's sick :(