In August 2016 Armentrout, then 39, was in the midst of life as a law enforcement officer in northern Colorado when he began experiencing fatigue and saw blood in his stool. The tiredness was a puzzle to a guy who moved from high school sports in his native Omaha to a college career as an offensive lineman for the University of South Dakota’s football team and a discus thrower with the school’s track-and-field unit.