First things first: You need a firearm. The time for "common sense gun control" went out the window the second grandpa came back from the afterlife to make a sandwich out of your face. No matter what your political stance was before the uprising, you fucking love the Second Amendment now. You want the biggest, shiniest, loudest monstrosity possible. If there's a gun that shoots a thousand bullets a second; that's great. If there's one that shoots a thousand flaming bullets a second; even better! If there's a gun that shoots out other guns that all fire thousands of flaming bullets in mere seconds--like some sort of pyramid scheme comprised entirely of shredding death infernos--well, that would be just dandy. But even if you already have the god-king of firearms at your disposal, you're still not ready. You need to arm everybody in your group, you need spares just in case and you need ammo. In short, you need to get to the gun store.
The only problem being: So does everybody else.
The closest gun shop to your house is also the closest gun shop to a thousand other people's houses, and at least a few dozen of them are going to get there before you. Assuming that the place isn't clean out--probably because the shop is either locked down like a fortress, or because the owners are barricaded inside and would rather like to keep their livelihood and defensive measures, thanks--you still need to get your arsenal. See, owners of gun stores tend to like guns, and people that like guns not only generally want to keep them, but are also quite capable of using them.
"You can have my gun... when you come down to my place of business and ask politely. I've got a lot, take one!"