That really sucks. I'm not sure what to think of the story, but if it was truly an accident then more's the shame.
I only ever handle my guns to oil them every once in a while, or when we're going shooting (which is unfortunately quite rare). Therefore we're not usually at risk for them falling off high things because they're always in storage, empty. The one thing we DO keep loaded is the home defense shotgun, and it's law that everyone tip-toe around it regardless of whether it's empty or not (it's usually empty with one in the magazine, several on the butt stock shell caddy, and the thumb safety engaged).
I'll definitely have to remember to be more careful when I get my CHL. I wouldn't be able to live with myself shooting ANYONE accidentally because I dropped my gun.