Was 'Martin' a first or last name for this man? The index shows a total of 7,220 possibilities for a Confederate soldier with the last name Martin. If I understand, you suggested that he may have an entirely different name. A 'runner' might be a civilian employee, so that doesn't help either. How would it be possible to narrow the search for this person?

In 19th century America, men threatened with deadly force were usually about to be shot or hung. I've never heard of anyone being threatened with beheading during the Civil War. Are you sure about this story?