Did I do something wrong for him to walk away?

I really don't understand why this guy acts like this, when ever I come to the park ( where we usually meet) with my friends he keeps looking at me and smiles, once he even came up to me and sat next to me, he kept looking at me but didn't say a word. This went on for about 2 months. I know I should have said something to him by now but I'm not sure if he likes me, I really like him but am affraid that he does not feel the same. Lately when ever I come where he is he just looks at me and walks away, I really don't understand why he went away, pls tell me why would he walk away