More than likely the tool the man was using was a post hole digger. I'm speculating but I've used one and I can't think of what else it could be. He was probably digging post holes for a fence. When you strike rock with the blades of the digger it creates a spark. Barbed wire fencing fundamentally changed and tamed the "wild west" and the North American prairie. Once fences were erected it was no longer open range. It was the end of the huge cattle drives from Texas to the northern prairies, the end of free roaming buffalo, the end of the cowboy and the end of the frontier itself. A great book on the subject is Cattle Kingdom: The Hidden History of the Cowboy West by Christopher Knowlton. I've also read books about mountain men and pioneers which discuss the subject. Many of Larry McMurtry's books also attempt to demythologize our idea of the cowboy.
In All the Pretty Horses, Mccarthy wrote, "What is constant in history is greed and foolishness and the love of blood." Evil and "prophets of destruction" are common in McCarthy's novels - e.g. Judge Holden, Anton Chigurh, cannibal gangs in The Road. One of the morals I've gleaned from McCarthy's books is to never underestimate evil. There are "true and living prophets of destruction" in the world and they are not to be trifled with. Usually the characters in his novels meet a violent end when they allow greed or vengeance take them down a path of no return - and there is only one path in our lives and we can never return on it or start over. In No Country for Old Men, Llewellyn Moss says, "Your notions about startin over. You don't start over... Ever step you take is forever. You can't make it go away. None of it." Later in that same book Anton Chigurh says, "The prospect of outsized profits leads people to exaggerate their own capabilities. In their minds. They pretend to themselves that they are in control of events where perhaps they are not. And it is always one's stance upon uncertain ground that invites the attentions of one's enemies. Or discourages it."
Be careful what you wish for and how you seek it. Do not assume you can dip your toe in evil and not be consumed by it.
Mccarthy is so dark... and so good!