In the manual there is usually a statement, or series of statements that say:

1. Treat every gun as if it is loaded.
2. Never let the muzzle point at anything you don't want to kill or destroy.
3. Keep your finger off the trigger until you are ready to fire.
4. Know your target and what is behind it.

If he would have followed #'s 1 & 2 he wouldn't have made the news.