Sorry it carbon monoxide not C02. A gas leak can cause that
perhaps they had a trannie female/lgbtq+ extremist as a temporary housekeeper or maid service? poisoned by their dog walker?
Carbon monoxide is a product of natural gas combustion. If it was CO, it would have been an exhaust-side leak. Natural gas accumulation can also lead to unconsciousness and death, but the smell is a give-away. Seems that if they had an automatic heater that a supply-side leak would have 1) been detectable by odor, and 2) led to an explosion due to the appliances pilot light.
“Sorry it carbon monoxide not C02. A gas leak can cause that”
Gas leaks do not produce CO.