Sometimes, the elderly can get paranoid and fearful about things that are going on around them. One of the articles mentioned that he has cancer. When an elderly person acts out like this, I always wonder if they have family nearby that were aware of how agitated their father or grandfather had become.
Anyway, health issues can cause people to behave irrationally, as can certain medications.
If you google "man shoots neighbor", it is shocking how often neighbor turns against neighbor over the most ridiculous things, mostly dogs, it seems!
I was born to be a pessimist. My blood type is B Negative.