Okay, okay guys, this thread is getting silly. Yukirisohoma, the suggestion to put feces into the lad's letter box was clearly a joke - I'd strongly advise you not to do anything like that to him. He hasn't even done anything wrong, you're the one that walked into the bathroom. Okay, sure, it was partially his fault for not locking the door - but we really need to "zoom out" here and see the bigger picture. What happened was a very small incident, an accident of fate. You happened to be walking into the bathroom at the same time that he was inside. Big deal, this sort of stuff happens all the time, and you're going to have to learn to understand that. He's not going to hate you because of this, but if you continue acting strange around him, running away from him, biting him, and ignoring him, he will begin to hate you. My advice for you would be to just approach him, say hi, ask him how he is, and then say something like "oh, sorry about the other day when I walked in the bathroom whilst you were in there...I felt really bad about it", and then he'll be all like "oh, hey, don't worry about, accidents happen". Sometimes you just need to see things for what they are, and realise that incidents like these don't really matter in the grander scheme of things. There was no malice intended on either side, so neither of you have any reason to feel ashamed.
Good luck Yukrisohoma, I sincerely hope that everything works out for you.