I didn't think he went there for drugs until his confession today. A niggling part of me doesn't believe what he is saying 100%, I just don't know really. Obviously there is truth in there but it's all a game to him. I also thought he was a nighttime prowler and believe it more so now, I agree there is strong probability he had been there before. If that is what happened then why would he bother to take the knife in the first place.?