I hope that there is a Heaven for dogs. Some preachers claim that animals just die while others claim that they go to some kind of heavenly realm. I see Biblical arguments for both sides, so all I can do is pray about it.
Perhaps the owner should have had two sets of keys, locking the first key inside the running van, a/c on and windows up, doors locked. When it is cold out (-30F is not uncommon in Calgary), I often start the car, leaving the engine running, and lock the doors with the key in the ignition. I then go inside, keeping an eye on the car. Once it has warmed up enough for the frost to clear from the window, I use the second key to open the door and drive away.
This is something that has always puzzled me, i.e., people who have but one set of keys. I never have fewer than two keys to my car, often three.
Not doing this helps ensure that one day you'll lock yourself out of your car.