well, looks like he cheated the system. I don't how he did that, but Stunna said that he'll post an article about it soon.
I was there when he won the first 1k and some people told the admins that they should check those bets thoroughly.. guess they didn't check enough
He apparently cheated by knowing his server seed. Once you know that, you can calculate what your future rolls will be.
Checking his rolls wouldn't have shown anything other than that he guessed 'hi' or 'lo' correctly more than the expected number of times. Everything would have checked out. Cheating using the server seed looks exactly the same as just "getting lucky". So long as you're careful (like Hufflepuff) and don't make it too obvious (like Robbin Hood) it's impossible to tell the difference between cheating and getting lucky.