Sounds like a sheriff that doesn't know Texas livestock rules...you have the right to protect livestock in Texas; however with that in mind they have to "really" be in danger not just loitering around your property, I believe they would have to be attacking. I love animals, showed and rescued dogs and have owned so many different types of animals. If you want to free range your chickens the same rules follow as for dog people. Keep them in a fence, I'm tired of seeing chickens roaming all over a yard with no fence holding them in.
Do the chickens roam in your yard?
I let my Ladies out for 5 years to roam in my yard. they stayed in the boundaries set with them as pullets and have never gone in the front of my house or the neighbors. Until we got new neighbors who have trouble keeping their animals at home They were very happy. They have a coop and run for evening and were in the yard while I was home. no fence that is why we established boundaries early on.