If his brain could function enough to make it to each show, and to wrestle a match, then I don't think that whole brain thing is an excuse. How come we never heard about him snapping on other people? I had read an article disputing that whole brain thing, I'll look for it...
My grandfather had alzheimers when he died, he was past 80 and he barely even knew who was coming to visit him. Hardly in any condition to kill 2 people, place some bibles next to them, text some friends about where to find them, and then kill himself.
I think he was just fed up with his home life and was frustrated about his kid's condition...to him it was mercy killings. Shit we will never know.