Ricochet by Thom Nicholson (Man Killer Series, Book 2) by Books in Motion.com

BLOOD MONEY! Theres a three-thousand dollar bounty on James Bennetts head, and Marty Keller intends to collect it. Deep in the Oklahoma badlands, Keller pins down his quarry with warning shots, but a ricocheting bullet strikes Bennett in the back and mortally wounds him. Keller returns to Fort Wayne to collect his reward, only to be branded a back shooter by the townsfolk. Then, to his surprise, Bennetts widow pleads with him to escort her and her young son to their new home in Wyoming Territory. As he sets out to lead them across countless miles of mountains and prairies, Keller is determined to protect his charges from any danger that may befall them both natural and human.