What would you do

[BLB68]

If they aren't trying to move me to a secondary location, then they can go about robbing the store undisturbed.

Moving to a secondary location? Not going to happen.

 

[Pussywillow]

I just know I'll be avoiding T-Mobile stores from now on.

 

[kingcheese]

If they where close to each other, and i only had one way out, you could bet id take my chances shooting, if there was a second exit, id run

 

[mr.trooper]

Most cellular stores use very open floor plans - virtually no cover or concealment at all.

4 BGs with guns in a relatively small and open space ... sounds like a situation that would probably get everyone present injured or killed.

I think the most viable course of action is to keep things as calm as possible, and only start shooting as a last resort - and shooting your way to a door / through a window to escape. Escape would be the only feasible option.