Guys, what does this mean?

I like a guy in the summer program I volunteer at, but he's a year and a grade older which makes me think he might see me as a kid. I don't really pay any attention to him because I don't want him to know I like him. He never really talked to me before, but he seemed to like messing with me. He also stole my phone and made me hunt for it in his pockets, but when I asked him if he saw my phone, he looked uncomfortable and serious even though he was just playing around. In addition he played keep away with my phone, told the kids to chase me, steal my shoes, and tie them together. He told someone that he thought it was fun to mess with me. Once, he was playing basketball and everyone was devoting a shot to someone else. Someone brought up the fact that I used to know him in 6th grade, and that he had cornrows. My friend said he made fun of me for being a creeper, but then devoted two shots to me, which was more than what he devoted to anyone else. But since two weeks ago, he's been more and more cold towards me. Nothing about me has changed except for a hair cut, but he acts annoyed whenever he's around me. He glares at me sometimes and he ignores me completely, except when someone else is making fun of me (then he'd join in). I'm not sure if this is relevant but this is also around the time rumors that I was going out with another guy were circulating. He also told me to shut up and snapped at me when the guy and I were messing around. He also usually makes eye contact with people and smiles at them when he talks, but he doesn't to me anymore. I'm also the only one he's treating like this. This doesn't seem like him since he's usually lay back and easygoing.