@peter Some diseases kill the elderly fast. Maybe the dog didn't die of what the two of them had and instead simply starved because of a closed household. We don't know how long they were out of contact, just that someone eventually asked for a welfare check.
I'm just saying it could be a lot of things, not just carbon monoxide poisoning (although that seems to fit the very few available facts well too).
Wonder if there will be a public determination of cause of death. Not sure on local laws.