For sure. A guy driving down the road in a car may or may not warrant much LE response. But some tree trimmers reacting to some skin art certainly will.The thoroughness of the investigation depends on the circumstances.
I would not have called LE. You don't know for sure he had a gun. You just think he did. I am not keen on bringing LE in to a situation based on mere guesses, particularly when their approach is to assume it's gospel truth without bothering to take the time to determine what really happened. What are the chances you "saw" a handgun because you thought he was making other firearm related gestures just before?
No harm, no foul? MYOB.