Complex sentence: They are successful until Principal Lewis finds them and threatens to sell them out, exposing Principal Lewis who owes the casino money, he blurts that the kids were counting cards and the casino owner orders that they all be shot.
Split into simpler sentences: They are successful until Principal Lewis finds them and threatens to sell them out, exposing Principal Lewis who owes the casino money. Lewis blurts that the kids were counting cards and the casino owner orders that they all be shot.