Ok, at 95 that would maybe be understandable, but his wife was considerably younger (63). And what about the dog?

And they were found in different rooms. Hackman apparently in a mudroom, and the wife in the bathroom.

Mine too, but the dog was found dead in its kennel. I'm no detective but most decent dog owners wouldn't do that if it was a planned thing.

Depends, they (or she) could've medicated it to death.

Assuming suicide was involved, if they had certain spiritual beliefs about life after death, they might have had an idea of the dog coming with them.