Missouri –
“Phelps County authorities have released the results of their investigation into the deaths of five people at a duplex near Rolla in June… two 43-year-old males, a 34-year-old male, a 21-year-old male and an 18-year-old female…the vehicle owner was listening to music on the car stereo in the garage and inadvertently went to bed without turning the car off…The owner was the first person to succumb to carbon monoxide poisoning, but by the next morning on June 19, the rest of the victims were found dead except for one survivor farthest away from the garage…carbon monoxide detectors, smoke detectors and motion detectors in the residence were turned off by the tenants.”
https://www.ozarksfirst.com/news/phelps-county-carbon-monoxide-deaths/