An attorney is responsible when he make someone signed papers and the person has Alzheimer's and is under strong medication?

My brother make my mother change/amended her trust, nominating himself as a only co-trustee taking me out of the trust. In original trust we are both, as my mother and father always wished! My brother hired a new lawyer and amended the original trust without my knowledge and 6(six) month later that my mother was diagnosed with Alzheimer's . She passed away a 2 months a go and even if there is a trust will my brother refused to do what's in. The trust ( that he amended) he control all the money. As well he took all my mither's belong ... How can an attorney accept do that??? It is not illegal what they did?? Since my mother was already with Alzheimer's and under very strong medication. I have letters of family members & neighbors to confirm what I'm saying! There is nothing I can do it???