If the car was filled with sand he could have safely discharged it in the vehicle. Or at least been safe while loading or unloading or playing with the loaded weapon (when they are known to just go off).
I am surprised he wasn't "cleaning" it at the time when it just "went off".
Yes, there certainly is something magical about cars and parking lots. Just ask anyone where you should unload and they will tell you "just unload it in the parking lot".
Ahhh, magical parking lots, always takes the sting out of bullet wounds.