Sounds to me like the young man made his decision, and now he has to live with the consequences of that decision.
He knew, when he decided to carry that weapon to protect himself, that one day he may be fired, for using that weapon. It is what it is. I'd say "Way to go young man. You're alive today because of your decision. You were looking for a job when Domino's hired you, so get back out there and find yourself another job".
My guess, is with all of this publicity, a business owner will step forward and offer him a better opportunity then driving the pizza delivery route.
Ya'll be safe.