Clarence Smoyer, now 94, was a gunner with the U.S. Army's 3rd Armored Division who'd come ashore in Normandy three weeks after D-Day, criss-crossed France and Belgium, and in March of 1945 fought to capture the German city of Cologne. There, during a firefight with a German tank, a car rounded a corner and was hit. Katharina Esser, a young girl, was wounded and later died. For years, Smoyer has played that scene (which was caught on film by an Army photographer) over and over, wondering if his shot killed Katharina. Seth Doane traveled with Smoyer to Cologne to revisit the site of the World War II battle, to meet with Katharina's relatives as well as the German soldier who was on the other side of that firefight. Doane also talks with Adam Makos, author of the book "Spearhead," about Smoyer's mission.