Our stolen air conditioning system

My family leases a hunting lodge about an hour away from our house. It is a beautiful property that is filled with trails, lakes, trees, and a variety of animals. In the middle of the property, there is a cabin that we stay in when we visit the property. We have invested a significant amount of money into the cabin to have it fully furnished and ready for use. A friend of ours even goes out to the property every two weeks to keep the grass cut as well. Last week, we decided to make a quick trip to the lodge. Upon arrival, we noticed that the air conditioning system in the front window of the cabin was missing. As we went to the door, we could see where someone had kicked it in. The thieves had gone through the entire cabin, and they stole all three air conditioning units that we had purchased for it. We also noticed that the grass had not been cut in several months. Obviously, the people who stole the air conditioning systems had seen how tall the grass was and assumed that the place had been vacated. Needless to say, we were not too happy with our friend who was supposed to be cutting the grass, and my brother even pointedly blamed him for the theft of the air conditioning systems. Personally, I only blame the people who stole the air conditioning units. I really can not understand what goes through the mind of a person like that. Why would they think it is morally acceptable to steal someone else’s air conditioning?