Trying to understand experiences from the past

I want to know what you think about this.... When i was younger in the 6th grade was listening to my teacher's lecture, i remember writing in my notebook word for word when suddenly without warning my seatmate who was sitting beside me suddenly grabbed my thigh. I looked at him and laughed, i thought he was just playing around so i just laughed. I remember how it was too. He was aggressively gripping my thigh for no reason. I never was friends with this person, we were only schoolmates, we never talked a lot only for groupwork, and most important detail i never dated this person. Looking back now i don't know what to feel, i'm so confused on how to feel about that experience, what was i supposed to react and say?? In this school we wear uniforms, the navy blue skirt would reach my ankles, and we would wear closed shoes and uniform polos and a necktie, same for the guys too only they wore pants. So i have no idea why he grabbed my thigh with no reason. I wasn't showing skin or even raising my skirt to be that high, he just did it for no reason. What am i supposed to feel?