I would probrably try to calmly aproach the child about it,  I think that I myself was a pretty resonable kid at that age (I did do some tracing and stuff back them but if someone came and talked to me about it I think I would understand it, I kinda of ashamed of those days...), and if it failed (as in if the kid was a spoiled brat) I would probrably try to report it. Would that traumatize the child? Maybe, but at least they would learn pretty soon the consequences of their actions XD (I tend to be quiet hot-headed in real life but I think in this case I would try to approach the issue as calmly as possible so that I would at least be able to keep my moral ground)