[DUMBGRUNT]

the carbon monoxide theory (due to proximity to the tailpipe of the cruiser)?

Unlikely on a maintained vehicle with a catalytic converter.

Possible, not probable.

[Svartalfiar]

the carbon monoxide theory (due to proximity to the tailpipe of the cruiser)?

Unlikely on a maintained vehicle with a catalytic converter.

Possible, not probable.

And not very likely in any outdoor environment. CO is lighter than air, so it tends to dissipate upwards. And any slight wind will whisk the exhaust away and provide completely fresh air. Watch other cars' exhausts when winter starts hitting - it's constantly drifting in various directions. He might have gotten a couple whiffs, but not nearly enough to do any damage.