if I had a gun store I'd put steel bars over the windows on the interior of the window/glass doors, put all guns away in safe at the end if the day (I know that that is a lot of work and extra pay for employees), and install wired security system and cameras with off site memory storage and back-up power.
thankfully i do not own a firearm dealer so i don't have that problem and most of my guns would be not worth stealing unless the crooks want mosins they can pawn for $50 or less or drive by russian pre-1950 style
i hope they find most of the firearms before they are used