As time goes on, people who don't have resources and don't oknow how to produce them would become feral. Most people in big cities don't even know how to plant basic food or which fruits can be eaten. A person with these skills could go to the desperate people and ask them to worrk together. You may think that staying in, by yourself, with guns would be a successful strategy, but it would not. The community around you must be stable, too. Sometimes, that means teaching people basic skills, so they focus on productive actions, instead of destructive actions. That's how I see it, anyway.