If,as it's been stated,that this man had dementia,then he'd have suffered a personality disorder,which includes violence and can be out of character with the sufferer.
I knew a very highly thought of past headmaster of a top school in its day,,where this poor soul had developed dementia and the violence he displayed was both upsetting to his family and also to those of us who looked after him.
He was,by nature,a very clever,calm character,until something snapped and he became a " monster ",trying to destroy everything in his path,even lashing out at the staff. Very frightening to see and be a part of. His temper was awful,,poor man used to push us aside to " line his pupils up ready to get on the coach "
I would imagine that even his family went through hell during his illness.