losing a tooth, not the good way

My five year old lost his second tooth the other day. He'd lost the first a while back, one of the lower middle ones. The tooth next to it had been loose for quite a while. I never got the whole story from him or his older brother. It must have been done jokingly but the kid took his fist and literally knocked his own loose tooth out. No tears, no arguments, just a five year old knocking out his tooth. Not sure if I should laugh or cry on this one.