Some more info...
-My title is wrong, it was quarter finals, not semi finals.
-It was a best of 3 series, Aris had won the first game. If this guy didn't score this own basket buzzer beater, Kifisia would have tied the series 1-1 and would have a chance for the break to advance. Aris won at 2nd OT so also won the series 2-0. So this was a critical basket.
-There is much legal discussion. According to FIBA rules, own baskets count only when they were not intended, e.g. trying to rebound. In this case, he clearly wanted to score the basket, but he didn't want to score an own basket. So was it intended or not? Referees called it not-deliberate so they counted it ( i agree ) , however you see the legal 'leak'.
Heh, crazy. Check out his opponent , he LOLs in his face immediately.