Setting: Gun store/shooting range. Hallway entering the place is about 20 feet long, a perfect bullet funnel. Occupants: Four staff members (two off duty cops, two employees, all of them open carrying). About 4 range members in the general area of the retail area. Situation: I'm standing in the waiting room to the range next to the retail area when I see people drawing guns, and I hear "Drop the f***ing gun! I'll f***ing shoot your **s if you don't drop the f***ing gun! Drop the f***ing gun now!". People are taking cover, one of the cops is taking a flanking position to the hallway. Out of my eyesight the BG had pulled a rifle out from concealment on his person. One of the off duty cops recognized him as a perp he'd gotten in a fight with previously after he was arresting him and the BG took a swing at him. Cop closest to me tells me to get into the other room and take cover, which I do with my friend I'm with. We haven't drawn, but my hands on my GLOCK and his hand is on his. Everyone in the main area is behind counters or walls, pistols drawn. Perp curses, turns around to leave... and one of the cops says he recognizes it as a BB gun as he used to own a similar model when he was a kid. I went into the range after he left, so I'm not sure what went down afterwards, but they called the police on him and I'm assuming he was caught. Freaking idiot. We have an SOP at the range that CCW holders are to let staff deal with the problem if it develops, and not interfere unless we're in direct immediate danger. I was in the other room out of the line of fire, so I didn't draw, but I was ready to do so. I was also positioning myself to drag the cop out of the line of fire if he went down. We had an MP5 and AR-15 in a range bag next to my friend, but I didn't make a move towards it; I decided instead to expedite my way to cover. I figured if shots were fired, I needed a pistol NOW, and it wasn't worth the time opening the range bag, digging for the mags, etc. It was pointed out to me I should have shot him in self defense; I figured if the cops weren't firing it wasn't my place to. Shooting a BG when there are two cops with drawn guns but holding fire is IMO a situation where a prosecutor would feed me to the hounds. As far as the long guns, both were my buddies (I only brought pistols). Didn't know where stuff was in his range bag, just what was in it. Didn't know if the mags were in separate side compartments, etc. I figured if anything only the MP5 would be of use (the AR-15 would have serious over-penetration issues, as well as IMO 5.56 FMJ being an inferior SD round compared to 9mm JHP). Additionally, the MP5 is a lot easier to fire rapid fire (any decent shooter can punch quarters within 7 yards). Thoughts/comments welcome. Lesson learned: always be vigilant.