[hinkley]

The article I read said no gas leak or CO was found.

However I don't believe that one person being found dead near an open door is evidence of no gases. I would take it as the opposite. Something happens, one of them almost makes it out but either blacks out at the open door before getting fresh air or, like in the CO case, once exposed the damage is done.

That said, the bigger curiosity is one dead dog and two small, live ones. If you have people poisoned by food, and one animal with food anxiety, that's a recipe for one dead dog and multiple dead people and other household animals wondering what the hell just happened. If you have people and animals poisoned by a gas... Unless it was lighter than air it should have affected the small dogs as well, unless they were napping somewhere outside of the immediate danger.

(The GSD could also have died from eating the prescription pills on the ground and it's only a coincidental death rather than common cause)