I️ caught my sons friend grabbing his private parts.

Monday morning I was taking my son and his friend to school. My son is 7 and his friend is 9 turning 10 this summer. They have recently became friends. They are neighbors and his mom and myself get along pretty well. His friend likes to play rough and when I see him playing rough I call him out on it (nicely but firmly). At times I feel like he may be a bit of a bully but my son seems to like to have him over and I always have an eye out on the 2 of them.Yesterday on the way to school I hear his friend say “what if I do this?!?” And grabbed his private parts. I was able to see him do this. I got a quick glance at the situation before he got out of his seat to kinda cover that he was going to his private parts. But I saw it before he could hide it. I called him out on it and asked my son what happened? And he replied by saying “he touched my private parts”. His friend quickly denies it but I told him I saw it and there’s no point in lying.I’m not sure what the next steps are. I know I need to talk to his mom because something feels off, but now I also don’t feel comfortable having him over since they like to play in his room and I can’t always keep watch. Is this normal behavior?Edit: For some reason my phone doesn't write the word "I" correctly unless I use Gboard. via /r/Parenting http://ift.tt/2AcZsR2