The idea of justice is stupid, flawed, and leads everyone to think in odd ways in the first place. There is no justice, no deserving something, none of it. Nobody deserves, earns, or gets what they have, they simply are who they are and have what they have. Regardless of circumstances, we should always take the path that leads to the best for all of us. Regardless of if some people deserve better, or some people deserve worse, or some people deserve X or Y or Z. It's not about what you or others deserve, it's about doing what's best. Communism, for instance, would be a very fair system. We all live well, and nobody has to live badly, we all get what we need to live and are free to contribute to the system. However, it's not what works best. Capitalism is.
Assuming any outcome is possible? Society figures out what caused the person to take that action, fixes the person to the point where they no longer feel they will, and will not commit crimes in the future, and forgives that person of what they did. The storekeeper should probably get insurance payments. If the storekeeper dies, that sucks. Keeping a person locked up their whole lives doesn't bring them back, and locking them up won't fix why others do the thing in the first place.So what should happen to someone who burned down a store?