So today I got in a rather large fight with someone and later go home. When I reach home I turn on my Xbox to try to see if any of my friends are on it and what do I find? A message that says my account was last used from a different location and my avatar changed. I have given no one my Xbox password and no one has been in my house sense, unless a bandit did nothing but change my avatar. So that's the first reason I know it was this person. My second reason is of course the fight. And my final reason being how he has constantly bragged that he can hack people's Xbox accounts. So I'm about 95% sure it was him. While I have made my account the same as before and am not worried about him using the credit card, as I know he wouldn't do that, I'd appreciate if he received whatever punishment is usually given to people who go on other people's accounts.
So to review someone went on my account and changed my avatar, and could have done many more things. I know who this person is and I'd like them to get whatever punishment is needed, and I'd like to know if there is anyway I can change my Xbox account, while not my windows live account, as the latter belongs to my father. Any feedback would be appreciated, and I can provide more details such as his gamertag and confirmation information that I (well, my dad) own this account. Feedback would be appreciated.
EDIT: My profile information (motto, location, etc) was also edited. This 100% confirms it was this person as he is using a word only and two other of my friends who wouldn't do this would.