Property Lines

The question of the day is: How do you go about telling your neighbor they are a dumb ass, without completely alienating them? I really have no problem pissing off my neighbors, after all I called the animal control on our other neighbors. These new neighbors however have something we want so I would like to keep the lines of communication open. We have to have access to their property to get to the path that goes through the valley and our fire pit is sort of encroaching on their property. If they would have killed my son however; I don't think I would have worried about being charitable.
We obtained permission from them earlier in the year for the guys to hunt on their property. The boys were only hunting with a bow. We never ended up exchanging phone numbers, so the boys didn't let them know when they were hunting. Definitely a no no on our part. Bryan was sitting in the tree stand yesterday when a shot zinged past him on the right. Once he figured out what was going on, he started down the tree stand when a shot flew over his head. He said he thought about yelling out that he was down there, but he thought maybe they were actually shooting at him. He ran through the woods toward our house hoping and praying he would live to see 2009. So herein lies the dilemma. Clearly Bryan was on their property without their knowledge, however; the first rule in firearms safety is to know your target and what's beyond it. I don't think they had a target, and they were shooting from their balcony into the valley. For years, a lot of people have used that path in the valley for hiking and access to a pond for fishing. While they can do whatever they want on their property, they are being reckless. Bryan is going to go talk to them tonight so we will see if we have reasonable neighbors or if I'm going to have to move our fire pit.