In The Blue Spirit (epi13) when Aang was talking to Zuko he mentioned that he and his friend KUZON were always getting into trouble. Remember in that same episode admiral Zacho was saying that KUZON'S comet was going to return!!!!!!!!! If you have any theories why he did it PLEASE post. Here is my theory:Since he seemed so close with Aang when he suddenly went missing due to the air bender monks he got angry and sought revenge.