Firing a "warning shot" is still dangerous.  Perhaps he pointed it away from the tree trimmers, but that means, by definition, that he pointed his gun *towards* something (and possibly someONE) else.   Several hundred people are injured or killed each year by so-called "stray bullets".  They can travel through home walls and windows, they can damage cars and property.  Stray bullets are not inconsequential, and firing a "warning shot" is just as irresponsible (if not moreso) than firing AT something.  At least when you fire AT something, you are planning where that bullet will go.  His "warning shot" was neither innocent nor harmless.