I think he was standing too close to that shot gun when it blew up. The blast must have knocked something loose up stairs.

where i grew up nearly all ranchers carry their rifles in the back window of their pick-ups temps there in the summer are probably 120+(w/ windows rolled up) and in the winter -40 nearly every year. Sunlight wont hurt a gun.

Besides, how can you shoot it at the range if it's sitting in the case?