I found out that my 8yo has been spending time with an 18yo high school student

Apologies if I make any mistakes while typing this, English is not my native language.I'm turning here in need of some advice. My husband and I had a moment of panic yesterday when our 8yo son casually admitted to "hanging out" with an 18yo high school boy. He told us that they've met during recess. It's not impossible, the primary school and high school are located near one another. We live in a small town. However, I don't understand why any student in their final year of high school would seek out 8yo friends?From son's perspective, they do typical friends' things during recess: talk about school and family, eat together, play basketball. He says the older boy has bought him fast food and the stickers he collects, which I especially don't like. My husband also believes that's suspicious. We told our son he can't accept gifts from this person anymore, but he doesn't understand our concerns.Obviously, I don't want them to spend time together anymore. However, I'm not sure what the best way to go about this situation is. I don't want to scare my son, or potentially raise panic about something harmless (I'm going to ask around about this boy and his family, though). Should we warn our son's teachers/principal of the situation? Raise concerns with the older boy's high school staff? Talk to this student or his family?Thanks for any help! via /r/Parenting http://bit.ly/2UrXZNf