Guys: Why would a guy keep acting mean towards me?

So there is a guy at my gym, pretty much we see each other everyday because we have the same coach. At first I was always greeting him and being polite because we literally work out in the same field everyday. Anyway, at first he would greet me but then he started avoiding me and acting distant, I thought he might be busy bc he is always on his phone. So today, one of my soccer balls landed on his side of the field and he didn’t pass it back (like he was right in front of it and looked up to me and yet he didn’t pass it back). So when I went to get it, one of his balls landed on my side of the field and I looked at him and passed back the ball to him…but he just looked at me and turned away to pretended he didn’t see me giving it back and said nothing.. not even a thank you. I don’t expect to get his attention, but I am curious to know why would a guy act this way when I’m being nice and polite to him? Why would he be mean?
Guys: Why would a guy keep acting mean towards me?
Guys: Why would a guy keep acting mean towards me?
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