I'll have to say I hated the idea of the little plastic empty chamber indicators when I first saw them - but they do a lot to prevent this sort of incident and also why a lot of ranges now have a 'bolt and mag out before bagging the firearm' rule in place now. Seen more of this than you'd think, and also been in several shops looking at .303's and had the habit for a while of checking the but trap out. You could fit 2 rounds of CAC 'clipped tip' up there and I found about 4 or 5 rifles with the spares still in place. Shop owners would go funny shades of grey and green on that one...
As far as the scope, having been checked out a couple of times it isn't nice... Although a couple of times I've been trying to locate the source of movement and sound through the scope having seen animals break and while wondering why and trying to spot them I've seen someone walking through the area that was the person that spooked them. It's not ideal and should never be done as a deliberate action but especially in heavily trafficked areas it's inevitable. There's an entire 'safe practice' thing that goes along with the 'pointing of rifle' rule - including keeping your finger off the trigger and outside the trigger guard until you've positively identified your target!
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