Oklahoma St had the ball with 4 seconds left and it was 4th down. They do max protect and throw a bomb to run out clock, but fail to send a receiver down the field. So everyone thought the game was over. Refs decide to call intentional grounding, which gave the ball to CMU at the 50 with no time on clock. They throw a bomb to the 5, caught by CMU, lateral to another player and he runs it in for a TD.
Mike Peraria (ref guy on fox) just said the rule says no extension game on offensive penalties that have loss of down. So CMU gets a bit of a gift, but big mistake for OSU either way. And they can't stop a hail mary...