If we are talking about a full collapse of society, food and ammo wont even be enough. A lot of people will act violent and die, out of desperation, and also out of lack of moral fiber or ability to produce for themselves, and they will die early. But in full chaos without any law or authority, people ban together in packs and hordes, and they also get clever. They will take resources they need, including fuel, and they will use their numbers and speed to their advantage, overwhelming people who think they can just take potshots with a scope.
Groups (gangs, hordes, whatever) will get bigger, in order to fend off rival groups. Thus, you will inevitably end up with war-lords holding territories. Once that happens, your little family commune with makeshift walls and line-of-sight defenses wont last. War-lords will fall, and territories will get bigger, but the bloodshed will turn into genocide.
All of this, of course, is moot.
If the SHTF, and the problem isn’t global, then you will inevitably have UN and foreign “peace keeping” boots on our soil.
you think godly people won’t also band together to fight them off?