Gundown! (A Breed Western #20). Breed, #20

Terra Verde had begun as a trading-post and grown to be a town. It was not a large town but it was big by New Mexico standards, and it was big enough to make one man rich. Terra Verde belonged to rancher Daniel Yates. He had wealth and power - and he had a son, Will. Will fancied himself as a man with fast fists and a faster gun. When the half-breed came into town, Will thought he looked like a challenge for a shootist.
But Will was about to make a mistake, a bad mistake that would it change his life for the worse ... permanently. And the Yates family were going to get Breed for that, whatever the price.