Both sides of this argument are being dense for the sake of winning the argument.
Thieves commonly use fake guns because they have zero intention of actually harming someone and because they'll get more lenient sentencing when caught. That being said, nobody involved in this situation knew the guns were fake and everybody acted accordingly: assume they are real.
The security guard did the right thing in shooting them because they were pointing something he assumed was a real gun both at the cashier and himself. He also stopped shooting once the criminals were incapacitated. 10/10 job as far as I'm concerned.
That being said, it's true that neither the cashier or the guard were in any real danger, because the thieves didn't have any fucking guns. It's not difficult to see this, so why is everyone being so purposefully dense?
Im being "dense" cause a pineapple wants to change definitions to fit his trolling aspect.
Also the only reason we know no one was in danger was because of a thing called hindsight ---