Airboss, (who wasn't a lawyer, and neither am I) described the situation as follows:
In Texas, if your property is surrounded by a fence designed to prevent the movement of livestock, trespassers are fair targets after dark.
Also, if you neighbor asks you to look after his property when he's gone, that also makes trespassers on his property fair game. Now, it's exactly 83 yards from my porch to my neighbors, and he has asked me to look after the place.....