They failed my 95 year old Mother who my brother was isolating from our family & friends and also moving our family estate money around with a power of attorney. Took 4 months of phone calls they ignored us, she died suddenly right after they went out to the house and still they talked to anyone. I don't know how she died and I know my brother has a history of abuse.
It sounds as tho they may have investigated and found nothing out of order in your care of your mother.
In any case, your mother is gone now. It is too late for you to make complaints I would think.
If you feel you have evidence of wrongdoing against your mother from ANYONE take your EVIDENCE (and be certain you HAVE said evidence) to an elder law attorney.
This sounds more like a brother against a sister and the brother was chosen to act for your Mother to my mind. Of course we here cannot know the details of this, are hearing one side, and very little of that.
I can only suggest that you have Sheriffs, police, DAs and Elder Law or criminal attorneys where you live. You should contact them and see what options you have.
You can contact your county representative (called county supervisors here) and ask how to lodge a complaint against APS.
What you can do if Mom has an estate is eventually ask for an accting of the POA even if that is the Executor. You are probably going to need a lawyer. And you may not be able to contest until the Probate accting is done that you sign. The POA is required to keep good records. The Executor is to follow the Will.
As POA your brother was probably given the responsibility of managing Moms "estate money" around but it should be done to increase the estate financially not decrease.
If you thought there was "foul play" in Moms death you could have requested an autopsy at ur expense.
I agree with those who directed you to speak to the police. You are grieving for your mom’s loss and you want answers to your questions. I hope that you will receive whatever you need in your life to acquire some sort of peace.
I am sorry that you have had such a difficult time with your brother.
IF you want to do anything - my suggestion is to contact your state rep or senator and share your story, asking them for a response from APS in your state. Secondly, try (it will likely be difficult) to share your story with a reporter or journalist. Appealing to the agency itself, or even their OIG (Office of the Inspector General) is unlikely to be anything more than massively frustrating and disappointing.
I wish I had better news.
Lets say APS does a well check. They go in and Mom seems fine. They tell her why they are there. They tell her someone is worried about her and she says she is fine. They ask if brother is abusing her, she says no. They make sure there is enough food and place is relatively clean and they leave. They can't do anything if Mom says she is OK.
I see your profile says Mom had Dementia. I know its expensive but you could have gone to court for guardianship which would have overridden brothers POA. Then you could have researched your claims and if u where correct, sued him. You could have used Moms money for guardianship once you were in control.