Let me get this straight, a couple of guys are sitting talking in a room, while unknown to them an idiot actually moves into a kill house with a loaded weapon and you expected any other outcome than someone getting shot?
Huh...
Sounds like a long chain of bad decision making process.
You forgot the part about it being a low light/no light drill.
"Praise be to our prophet, John Moses Browning, who hath bestowed upon us the new testament of shooting. Delivered unto us, his disciples, on 29 March 1911 A.D."