Whys he get so frusterated?

So theres this guy.. whom im guessing has feelings for me. he USED to stare at me, now he just looks at me small eyed like...ever sense he saw me hug the other guy in gym cl that one day.he got all jealous.. (his friends say he isn't even jealous type..why is jealous with me?)... so when i dont notice him.. he gets all frustrated..and sighs..and looks at me then looks down ish. this happened twice. when i was texting another time when i was just walking.. he looks at me small eyed and looks to the side. then down. whys he get so "Hoo humm" like with me.??