Yeah an appraisal crew was there because OP is in the process of buying out the shares of two family members. It's only fair that they know what the property is worth.
Second, I understand the desire to see why an unfamiliar vehicle is snooping around property you have a control over. I grew up on a farm and we had to run folks off our property a few times. One group kept spotlighting deer on a property, and they would always drive off if they saw one of us coming. 3 or 4 times of this going on, I went with another laborer and had him approach the vehicle while the property owner and I blocked the path and called the game warden. WE DID NOT GET OUT WITH THEM WITH GUNS DISPLAYED! NOR DID WE HAVE ONE ON OUR SIDE. They didn't appreciate the fact that we blocked them in, and we expressed that we didn't appreciate them illegally hunting on the property. They had hunting rifles, and were a little agitated, but were happy to leave peacefully if they agreed to not come back.
The point is, I kind of understand not automatically calling 911 without investigating first. In rural areas response time can be up to an hour for a low priority call. Plus it seems like things were different 20 or 30 years ago. You could get in a confrontation without automatically fearing for your life and displaying a firearm, for instance.