Real world experience...
I've been in a few Denny's late at night when people started having issues with staff or each other. A few fights have broken out, and one person did leave saying they were, "going for my gun" -- that time, the waitress looked really stressed but they didn't close the doors. When we started talking to her, she said, "I'm just a little jumpy, since we had a guy last night who actually did come back with a gun. Usually they don't. It was a major stink and the restaurant was closed for 4 hours."
The strangest semi-related scene was a few years ago (1999 now that I think about it) when a friend and I were sitting in the local Jack in the Box having a snack at about 10:30PM. There were a lot of people around, a fact I attributed at the time to the local cheap movie theater just letting out or something.
Suddenly, we see a van haul ass across the parking lot drive through a crowd of people, nearly hitting some. The van stops, and the driver (no shirt, tats, yadda yadda) gets out and runs over to one person in the crowd and shoves them to the ground. A start of a fight ensues, but a bunch of other people, maybe 20-30, rush in, and they start pushing the van driver. Van driver's shoving victim gets up, and words are exchanged... more people are entering the parking lot, almost exactly as though this was an arranged meeting.
Another car, an old olds or the like, does the same "drive through the crowd" stunt... at this point the restaurant is full and people are staring out the window. There are maybe 50-60 people in the crowd outside, and more people are coming into the parking lot. The driver of the second car gets out, and he and the van driver start getting in each other's face and screaming. Inside the Jack in the Box a line of women form to use the restroom. The parking lot seems to have maybe 100 people, and more are coming in.
Van driver pulls a stainless steel revolver out of his pants and starts brandishing it... this was about 30 feet from the restaurant (there was a green area, a sidewalk, and a row of parked cars between us and them. At that point, restaurant employees lock all the doors (there were maybe 40 people inside at that point) and get on the phone. 911 I assume. It became a lot harder to see what was happening then because most of the people in the restaurant were crammed up against the windows watching the crowd. I was sitting there eating my onion rings -- I wasn't about to stand up to watch, but I could still see most of what was going on. The group of people was still growing and there was an active shoving match/low-key brawl going on... a bunch of people were kicking one guy, then more people showed up. A steady stream of people, mostly Hispanic women, came up to the doors and tried to come in. At the end, the mass of involved people was a churning and shoving amoeba about 150' wide and 250' long, with a nucleus of air and, I assume, the original fighters. Outside the main group were little pockets of people (i.e. us in the restaurant, and individuals or small groups standing around watching). I'd hesitate to estimate the exact number, but hundreds. The fringe of the group wrapped around the restaurant, but the main focus was a little ways off in a "road" part of the parking lot where there was more room for everyone to do whatever they were doing.
It continued that way for about 15 minutes, with a growing crowd that was starting to develop migration patterns with occasional new cars coming into the mix, bloody people leaving, and so on....then, suddenly, people on one side of the crowd all started running in every direction. The dispersal spread across the crowd like a wave, with people scattering as soon as they saw others scattering. Some walked off quickly, some ran. A few stayed. Oddly, the core group didn't break up, though some people were obviously trying to convince their friends to leave. It was about another 3-4 minutes from the time people started running until we saw why they were running, because at that point a bunch of cop cars raced into the parking lot.
So cop cars charge in, then more cop vehicles (vans and the like) show up, and cops run to catch certain individuals, including the guy who brandished the revolver. No real standoffs... he tried to get in his van and drive away but they stopped him. He got out of the van and allowed himself to be handcuffed. There was none of the "cops" style thuggishness on the part of the police. I was expecting to see a jackboot convention, but perhaps the fact that the police were outnumbered maybe 20:1 even after the crowd broke up kept them civilized. According to the news they arrested 5 people.
Overall, the doors were locked for about 35 minutes. Once the restaurant unlocked the doors, we went to our car and drove away. The next day, I called the person I was eating with and said, "Did that really happen?"
What did I do? In every case, I ate. Why? Even if somone started shooting, the odds of catching even a stray bullet were about as close as you can get to zero without being absolute zero. I had more concern for my safety on the drive home.
