My guess about what happened to Gene and Betsy

I hope this isn't too ghoulish to post this, but my guess about what happened is this:

She died suddenly from natural causes, like a heart attack, and then he was in such a state of grief and shock and confusion upon finding her that he attempted to leave to get help—hence him being in the mudroom—but suffered a fatal heart attack himself and died right there. One of the dogs happened to be in its crate at the time, and so died after 3-4 days of no water.

Perhaps she was simply unresponsive but not dead yet, and he was attempting to leave to get help (maybe not thinking about the phone when being in a state of shock) and got as far as the mud room.

He was 95, had issues with his heart for at least 20-25 years prior, and they had such a close and symbiotic relationship that it would not be surprising at all that her death would kill him.

Really sad, and my heart goes out to their family and friends.