I don't remember the venue, but a few years back some antigun folks were caught loading guns at a gun show, presumably in the hopes of causing an incident. Having said that, it's ultimately the owners responsibility to ensure unloaded guns!
I was present at a show when a negligent discharge happened, fortunately before opening. A dealer was showing his CCW to another vendor. He dropped the magazine, and handed it to the other dealer, who pointed it at the floor and pulled the trigger. Yup, one in the chamber!
We heard a loud bang, and my buddy and I looked at each other and said, "Oh yugo"! We were on the far side of the room, and I say a vendor near us, brushing dust off himself and looking up at the wall. The promoter walked into the room, and loudly asked if anyone was hurt? Everyone shook their heads, and he asked who fired the shot? Everyone pointed in the direction of the white faced guy holding the pistol! The promoter walked over, told both of them to pack up, and never come to one of his shows again.
I looked later, and there was a divot in the concrete, and a vendor on that aisle showed me the hole in his table skirt. He said the bullet missed hitting his wife in the leg by about a foot!