Several incidents come to mind. They all happened a number of years ago, so this "herding up, killing" is not new:
Bob's Big Boy restaurant: 4 employees herded into a walk-in freezer and shot to death.
A large shopping mall multi-movie theater complex: 4 employees herded into managers office and shot to death.
A small cellular phone business in a "strip" mall: 2 employees shot to death in rear storage room.
Another Bob's Big Boy restaurant: manager was shot to death while unlocking the office safe....only because he was trying to remove his wedding ring while he worked the combination of the safe.
In all of these incidents, the employees were not armed, and were subject to termination IF they were caught carrying a firearm at work.
In all of these incidents, the locations weren't in "bad" parts of town. In fact, they were all in relatively low crime "nice" areas.
In all of these incidents, the killings took place out of view of the public.
In all of these incidents, except for the manager trying to save his wedding ring from being stolen, the employees appeared to have fully complied with the demands of the shooter(s).
Even if you have 110% "situational awareness" of your surroundings, you may not be 100% "safe", no matter where you are.
Having brought up all of these items for you to ponder, I can only say that it's up to YOU, personally, to exercise your #1 "weapon"....your brain....and to realize that being "herded" into a back room or out of view might actually end up being a "slaughter". Use your "situational awareness", and don't get stuck in "gun mode only" as a way to survive! Think "What can I use as an effective ruse, or make-shift defensive 'weapon'?"
Lastly, an incident with a "happy ending"! A robber entered a crowded liquor store and pushed his way to the sales counter where he pulled out a sawed-off shotgun. The robber was wearing a ski mask. While the employee was emptying the cash register, a customer was able to "arm" himself with a bottle of wine from one of the racks. That customer was also able to sneak up on the robber and hit him solidly in the temple, which caused him to drop the shotgun and fall to the ground. A few other customers jumped on the robber, and the employee retrieved the shotgun.
I was a LEO at the time, and responded to the "Robbery in progress" radio call at the liquor store. My partner and I arrived within less than 2 minutes after the initial phone call. The suspect (robber) was definitely hurting, and even mouthed the words, "Kill me!"
The "hero"? A 19 year old illegal alien from Mexico! He was worried about his immigration status when we were conducting our initial investigation! Heck, I wanted to give him "instant" U.S. citizenship for what he had done! He DID, in fact, benefit from his heroism, for he was granted a "green card", and stayed in the USA to testify in the criminal trial. (He also got a case of beer....or so I heard....from the owner of the liquor store).
You have to admire someone like that! A wine bottle "weapon"? That was truly "situational awareness" at its best!