Aunt taking my deceased father’s money and possessions

Location: California (Los Angeles County)

My father passed away in early June from a stroke (his second one) and was taken off life support since the doctor told us he would not have anymore quality of life. I will admit I was not present in his life the last 9 years and because of this my aunt who was much closer to him believes she is entitled to his possessions including his money. This aunt and her immediate family in particular is the main reason why my father and I did not talk the last years of his life. It is also worth mentioning I am his only living child. My aunt just a couple days after he passed started taking out amounts of anywhere from $200-$400 out of his bank multiple times a day approximating to about 10k to this point. I was able to get a hold of his phone and discovered what my aunt was doing. I even found out she called the bank to close his account. My uncle said he thinks he overheard her talking to one of their sisters and he’s pretty sure she pretended to be me when closing the account. My father did not have a will however, I was a beneficiary under his life insurance( I’m pretty naive to legal matters so I don’t know if that makes sense). I went to the bank and they told me they couldn’t pull up any receipts of the transactions since the account was already closed out. I am set to pick up the rest of his belongings within the next couple of days. I asked my aunt if she wanted to keep anything and she told me no. Which to me means shes already taken what she wants. I understand there’s nothing I can do to prove she’s taken his possessions but I hate the idea that she is taking from him when she is not his next of kin and completely taking advantage of the fact that he’s passed away. If there’s anyway someone help me start a case (if there even is one) or at the very least point me in the right direction I would be very much appreciative. Thank you