No.Like you I need some proof of his own admission.
Seriously Lookout, if he is guilty of murder, is he going to say that he hated the fact that his mother gave money to the church or that he was afraid she would leave them money in her will? Why did he go looking for the will a few years prior to his parents deaths? It's not something I would EVER have considered doing with my own parents - usually the thought of their death, is something you would rather not think about and distribution of their wealth is an even worse consideration because in order to inherit, they would have to be dead.