The other boys follow. What are they supposed to do when grown man is dragging a boy away? They try to pull the boy free. Again no punches or kicks, just requests to "Let go of him."

The grown man then pulls out his gun and discharges it, still holding onto the first boy who is splayed across the bushes.  The children scatter in fear.

Watching the video a second time, before the shooting, you can also hear the boy complain that the grown man had tackled him for no reason. So apparently, even before the third boy tried to tackle/block the man, the man had done this first. Again, a reckless thing to do especially with a gun in your waist band.

What is the result of this man's aggressive actions over children stepping on his lawn on their way home from school? 

His neighborhood gets trashed by an angry community, his car and house windows get smashed, and he is facing a lawsuit. He has made many enemies.

With other ways to handle the situation, I would say he made very poor choices.