The guy slap too hard in training, he severely debilitate the other guy's head in the first strike, a tap on the back then, his hand did not let go after the impact, that is another kind of power. He should not be a teacher at the first place. Can cause internal injury. See the other guy is short of breath, face red and sitting down. He was not in good condition then, training should be stopped. But i am not a pro, i just know the student is really not doing well after the first hit.
Usually teacher likes to show how good by beating up their students but i disagree. It is how much you can make the student grow that make a great teacher.
Over