Guns are on Police Officers, Criminals, cultists (AKA Fanatics) and available from the hunting store.
Police Officers use Revolvers and .38 ammunition available as items. Sometimes a shotgun with 12 gauge ammunition.
Cultists have access to any level of guns since of their connections so they may have any available.
Guns and ammunition of most things are sold at the gun store but it seems like they have an exclusive client to the cultists. Good thinking will need to be used to get access to the inventory in there. Additional guns and ammunition available that are not used by the standard issue of police officers though it's not unheard of for the police to have confiscated various guns and weapons in evidence the players may be able to access with some good thinking or roleplay.
All other weapons such as a baseball bat, mop or box cutter are environment weapons that franz could offer to players if they're searching for items. Weapons are logically placed ie, "Baseball bat at a highschool" or "box cutter at the store" or "nailgun at the hardware store (essentially a gun alternative).