Absolutely the parents are at fault here, no doubt in my mind, it is up to them to teach their child to respect and treat animals properly, even though he is nine years old and should know better, he probably doesn't because his parents have not bothered.

Again do your best, and thank you for at least caring enough to come here and discuss it with us all and get advice, now go and act on it and help change that kitties life for the better OK.