Reddit reviews Gettysburg: A Journey in Time

You're probably thinking of William Frassanito's Gettysburg: A Journey In Time and subsequent books. Frassanito has written extensively on Civil War photography, and based on his findings the way the gun, hat, etc are placed in this photo it is most certainly staged. Many Civil War era photographers were interested in making images they could weave into a human interest story which would in turn sell more photos, albums of their work, etc. http://www.amazon.com/Gettysburg-Journey-William-A-Frassanito/dp/0939631970

Hey! I found the book!