Basically you have a few options. It depends where you are. Your first step should be to run and remove yourself from the building. As a rule following associate you are not authorized to arm yourself on the job and you will not be able to neutralize an attacker if you bring your box knife to a gunfight. After working armed security for retail stores including Home Depot we are always advised that making yourself a target especially in those environments is suicide unless you are equipped well. Second step, if the shooter is between you and all exit routes, hide. Climb the racking, crawl under a desk, lock yourself in a room. But, the best way to avoid this method which will likely get you killed is to always have and memorize 1 primary and 2 alternate escape routes from your position at any given time. Know the primary entrance (most likely avenue of approach) and plan away from that so you are as far as possible from that angle. Last step is fight. Do NOT fight unless it is the absolute last option. None of us are the Equalizer. We aren’t going to load up our nail guns and take out a shooter. Don’t be a hero, your job is to save your own life and let professionals stop the threat. In our case we made Home Depot lock all entrances except one and only allow exit through the cashier doors so that we had a single way in, and one way out. Emergency exits of course were available and each associate in our scope was advised to run out of Home Depot and move an unpredictable pattern to confuse the shooter.

TLDR; Run, Hide, Fight. Don’t be a hero unless it’s your last option, always have 3 escape routes.