Southwest Louisiana, Beauregard Parish, near a lake. It was up on a Chain link fence.
The kids chopped it's head off, I never saw the head! It was 30" long, shiney black on top, blunt at the tail (not a moccasin) but the strange part was the coloring underneath. It was alternating bar's of Rust colored scales. About 3/8ths of an inch in width, and ran from the midline, down under the belley, Stopping at the center of the belley. The Rust bar's were alternating. One from the left, and one from the right, from the snakes neck down to the Tail.
I looked in Louisiana snakes, LSU's library, and Herps of Texas. I also have another mystery for when we solve this one!