It's been established that the game is over, not at the "final buzzer," but when the officials leave the floor (NFHS 2-2-4 and 5-3). Two thoughts on this...
...
And now, we're coming down on this official for doing his job?
Apples and oranges. In one, the coach was committing an unsportsmanlike act after the horn. In the other, they were not.