A Boy of the Streets by Harvey Whitehill

A year after his mother's death, 15-year-old henry has his first run in with the law when he's caught stealing butter. He quickly picks up the new skills a boy needs to survive in this wild land, gambling, fast talking and, crucially, how to shoot. Harvey whitehill is a respected war veteran, well regarded by townsfolks and outlaws alike. He's sworn to tame silver city. And while he doesn't think anything much of it yet, he's just become the first man to arrest billy the kid.