What do I do if I think my father was taken advantage of financially by my sister who lived with him? There may have been elder abuse.

My dad had parkinsons with dementia and wasn't diagnosed with the dementia until he fell over a small chest in his bedroom and ended up in the hospital. My one sister lived with him and was supposed to be taking care of him. My brother and other sister were away for a weekend with our families on November 5th. My brother received a phone call that dad had fallen and my sister couldn't get him up so she called the paramedics. She called later to say he was fine and they got him back in bed. When we returned from our trip on Sunday, my brother and sister went to see him. When they got there, my sister was on her computer like nothing had happened and my dad was in bed in his room with the door closed. My brother said when he and our sister went up to see him, he was laying in a very uncomfortable position in bed with his head twisted and moaning that his back hurt. There was dried and wet urine on him. My brother called the paramedics. It happened to be the same ones that was at the house the previous day. They said they had to file a report yesterday and today because of the situation. My father was dehydrated when he got to the hospital and although he thought it was the 1970's, he was hungry and thirsty and kept saying the bad my sister wouldn't give him any food or water but the good my sister was real nice. We later came to find out that my sister may be mildly bi-polar and is supposed to be on medication. Also, my sister never came to see dad and never asked if anyone would take her (he was back and forth between the hospital and nursing home except the last 3 days before he died).

On December 3rd, dad passed away. We keep wondering how he could have gotten so bad so fast and wonder if he wasn't taking his medication and why he was laying in his own urine.

Upon going through my dad's finances, there are checks made payable to my sister's dentist which total over $5,500 and a check for $1,000 made payable to her where it's apparent that something was wrong when he signed it because his signature goes below the signature line. Also, he made a lot of checks out to himself that he cashed which didn't make sense. What does an 82 year old man who can barely get around do with $750 in cash in 4 days and there's nothing in the house to show for it? Dad was tight with his money and my brother had asked to borrow some from his inheritance for his divorce. My dad kept a record of all the checks, attorney invoices, and a list that states that he owes it. There is no problem her as he is fully aware he owes it and it will come out of his inheritance. Also, my other sister had asked to borrow $3,000 for her divorce about a year ago and my dad said he didn't have any money and Donna kept saying he didn't have any money yet this was around the time he was paying for my sister's dental work. Also, my sister has a pot habit. My dad had a total of about $140,000 between all his accounts. Also, we saw a statement for a $5,000 CD in my sister and my dad's name and we can't figure out where she got the money since she only received about $937 a month for disability. my sister decided to go to Rhode Island to live with her daughter until she can get an apartment and left with only 2 suitcases and the dog right before Christmas. She seemed to be in a big hurry to get out of the house.

I need an objective opinion as I feel I'm too close to the situation. Can anyone give me any suggestions? I apologize this is so long. Thank you.