I didn't like how the guy had his mouth open. I would have considered hitting him too. Nice to see he finally got put in his place.
I call fake. Just buy the way the keyboard keeps moving after it passes the guys face and you can also see his hair move because of the wind. And before falling the guy already has his arm out to get ready for when he falls back.
Yeah its most likely fake, but it's still funny regardless. The kid was smiling while the guy swung at him with the keyboard, my face would be the complete opposite.