Theory I have but can't prove is that a huge number of accidental gun deaths and suicides are murders that the cops are just too lazy to investigate https://people.com/human-interest/dog-shoots-kills-owner-freak-hunting-accident-kansas/
Dog Shoots and Kills His Owner, 32, in Freak Hunting Accident, Kansas Authorities Say

Officials in Kansas say a man has died after he was shot by his dog in a freak hunting accident

Peoplemag
Maybe in this case there's some really compelling evidence that the dog indeed somehow fired a shot and killed this guy. Feels extraordinarily improbable compared to the "another human being shot him then left" hypothetical though!

@mtsw people can be dumb with guns, but “put a loaded rifle in the cab with the safety off” strikes me as improbable. If nothing else, rifles are big and unwieldy. Having one point *at* the driver seems just implausible.

Most of the hunters I know would either use a case (good hunting rifles aren’t cheap), or would lay it horizontally, where a negligent discharge would strike the door.

Quick, someone check if he owed a cop money or something.