Longarm and the sharpshooter
(Book)

"His prisoner had help--but Longarm never saw who it was. The backshooter's bullet creased the nape of his neck, knocking him from his horse and rendering him unconscious. Eager to make his getaway, Alton Gray made a fatal error--he didn't take a moment to confirm that the lawman was dead. Now Deputy U.S. Marshal Custis Long is back on the trail of the runaway prisoner--and his ambushing accomplice. A corrupt town marshal and a wily woman of ill repute may lead him to the elusive escapee, but to finish the job he started, Longarm will have to stick his neck out one more time ..."--,from publisher's web site.