Just don't point it at anyone you don't intend to shoot. Way I was taught and should be the way no matter what.
ags
Exactly what I was taught, and what I used to teach other when I did shooting training and range safety training (civvie and cadets only). I would guess that the guy who set the weapon off in the demo fell for the old forgot-the-one-in-the-chamber fail. He probably checked the mag was empty but never finished the job by pulling the slide back.
Many years ago, whilst training cadets in weapon safety, I played a very cruel trick to ram home a point. Normally the cadets were taught to check the weapon was clear as soon as they got it from the Armourer (this was a VERY long time ago - these were Lee-Enfield Number Fours: .303 bolt-action rifles), but in this, their first lesson, I told them that they had been checked by the Armourer before being issued and that they should leave them alone. Having given them the ten minute spiel on the damage a high-velocity rifle round can do, I instructed them to open the bolts. Out of each one sprang a dummy round - very similar at first glance to real one. I thought at least one of the cadets was going to pass out. "That", I explained, "is why you
never take anyone else's word for a weapon being safe - you always check it yourself."
M