I have a feeling in your wife's case, he was ticked off about some silly little thing.
With my own father in law, however, I wish he HAD used the will as 'get-even time'. My brother in law raped his sisters and tried to rape my husband. He tortured them anytime he could get away with it until eventually mom and dad figured it out, and he was put away until he reached 18. When FIL split everything evenly, it was a real emotional issue for the siblings.
YIKES!
I guess evenly unless the money would got to a socio or phsycopath.
Basically my wife move to the west side of the country, in part to get away from the strange but interesting family antics.