To Do this he would have had to take the final shot, run across the entire 6th floor, stash the rifle, run down 4 flights of stairs, cross the entire 2nd floor to the coke machine, and purchase a coke in less than a minute. The Cops also stated he did not appear agitated or out of breath.
The question then becomes, was that possible or did the cop just not notice anything out of the ordinary. I make no claim either way, as I do not know 1. Oswalds physical description or 2. the mental state of a cop who was rushing into a building where they thought a gunman had just shot the President of the United States.
Make that Oswalds Physical condition.