I'm afraid it may come to that. We haven't had another incident yet but the family REALLY. Needs to make a decision on what to do with the old man...
If you shoot the old man's dog, make sure you do it well so it doesn't run home to die. Then take it out to the country and dump it over a secluded bridge for the coyotes and raccoons to clean up. Then, when asked, deny all knowledge.
If you can't do this, be prepared for a vendetta of unknown proportions from an old guy with time on his hands and a mind that is a half-bubble off plumb. While you are at work, or asleep, he could be up to all manner of mischief.
Might happen; might not. Just saying.
John