Ah I see a little better now.
I would suggest that your guilt over these facts are not warranted. The fact remains that these boys next door have repeatedly been causing trouble.
We all read of children going out and killing other people.... a recent one here in California...
http://www.mercurynews.com/ci_8520003?nclick_check=1
We all wonder what we can do about such tragic situations. We wonder about the child's parents in this article above situation. How do they feel?
How would your neighbors parents feel if their 13-year-old son did this to another of your neighbors?
How would you feel knowing that if you warned these people that their sons may be headed for real trouble if the current behavior does not stop?