Harry:
He stops talking to you. He crosses his arms over his chest, and gets this vacant expression when you talk to him. He ignores everything you say to him, not even looking at you, as he stares bitterly at the wall.
He won't answer you when you ask him a question, and he won't engage in conversation - at least, not right now. He's too mad for that, afraid that he'll end up bursting, saying something he didn't mean and making the situation all the worse. He doesn't want to hurt you, - even when he's this mad at you -, and he knows better than to open his mouth when he's mad, so he keeps it shut.