This violent land / William W. Johnstone with J. A. Johnstone.

Enhanced descriptions from Syndetics:

A western hero whose adventures embody the spirit of the American frontier, Smoke Jensen is bestselling author William W. Johnstone's most beloved creation. In his powerful new novel, Johnstone chronicles Smoke's early years. Before he went off in search of his father, long before he became a legend, Kirby Jensen was a young man trying to make a living with the gifts God gave him courage, cunning, and lightening with a gun.Kirby has just earned his first paying job as a Deputy U.S. Marshal for the Colorado Territory and is sent to Las Animas, where a band of ruthless outlaws has been robbing trains, cattle, banks and anything else they can get their hands on. In Las Animas, Kirby finds a sheriff too cowardly to face the outlaw leader Cole Dawson, whose six-gun has left a lot of good men dead. Young Kirby feels no such fear. He takes Dawson down fast. Then the real fight begins.