I would do that around my residence as well.
However, the term is used quit frequently on military bases. These installations have planned response teams normally ready on small and large bases. They want the intruder, criminal or shooter wandering around without all sorts of other uniformed and non uniformed persons out confusing the situation.
As most bases are training, permanent party, storage of equipment and the like, uniformed service people without the duty need to be armed are not armed. When you think about it it makes perfect sense to not have to draw an M-16 when you are changing the fuel filter of the fueling system of a cutter.
The base I am in and out of the last few years shot dead an “active shooter” who was an idiot car thief who would not stop just before I got here. They have no problem taking out the bad guys, but it isn’t a free for all.
Part of the reason for asking people to shelter in place is so the good guys won’t mistake the local residents as the bad guys.
Of what nationality was the gate crasher? Obvious he wasn’t a tea partier or that would have been the headline.