Most of the comments I've read thus far have had excellent advice. Being pro-active is of paramount importance, and I second any suggestion to start/maintain a neighborhood watch, alert the cops of any and all suspicious activity, keep your firearms and valuables secure.
If he thinks/knows you have guns he would most likely attempt to rob you when you're out of the house. I doubt he wants a direct confrontation, or has the spine for it. Don't let one rotten apple ruin the entire neighborhood for you, get the community together and don't try and tackle the issue on your own if you can help it.
You mentioned the boys guardians/relatives being inept, but you might also try and voice your concerns to them if you think it might help. Sometimes the realization that the neighborhood is actively looking at them can be a very strong deterrent for would-be burglars.
Be Safe and Good Luck