Perhaps a bit of clarification...
There are quite a few variables that are not mentioned here. Is the poster in active law enforcement--either full time or as a reserve/auxiliary officer? If not, are they well known to local LE?
Is the poster retired LE?
Is the poster on duty as a Security Officer?
If the answer is none of the above, then...well, let me put it to you all this way: If I am dispatched to a burg call, alarm or break in and I arrive and see you drawing a firearm--guess what? You just earned yourself some time in the prone position while I relieve you of your firearm, place you in restraints, and find out what you're doing.
Why, you might ask? After all, you are simply stepping up and trying to help...right?
Folks...I DON'T KNOW THAT. Neither I or any other officer knows that.
I do not know what you're doing. You might be a good guy. You might also be the armed lookout for those people inside. I just don't know.
And I'm sure not betting my life on you being the good guy until I find out for certain.
If it's sorted out fairly quickly, I am going to tell you to get your wife out of harm's way, and KEEP THAT DOGGONED GUN HOLSTERED for the time being.
Moreover, unless someone is in immediate danger, I am NOT going in there by myself. There are faster ways to commit suicide.
Finally, if I involve you at any stage of the process, guess what? I have now assumed full liability for your health and well being. I've also put my Department at liability.
Yeah, it stinks, but that's the way it is.
Would I ask the regular Joes and Janes for help if I needed it? Of course I will. And--if I or another officer is taking fire and someone engages the BG from defilade and takes them down, that's very well appreciated, thank you very much.
This is a building clearing scenario from another post...
Summary: you do NOT want to be the one standing there with a gun in your hand when we arrive on a hot call. Not a good choice...at all.