You can tell by the pattern and the scales that it's not a water moccasin which also have a distinct triangular head.
Compare the pattern of the snake in his picture to this one of a milk snake
http://www.umass.edu/nrec/snake_pit/pages/milk.html
Usually a milk snake has more red in it which is why I thought it might be a Pine snake but this looks like a young one and location might have something to do with it as well. A picture of the belly scales and pattern would have been a big help in identifying it.