“Why the first shot did not occur at or near Zapruder frame Z160.”
Reason Eight: Oswald’s Position in the Sniper’s Nest

As shown in the Secret Service re-enactment film, Oswald was back from the window to rest the rifle muzzle on the box he placed there for stability.  (See my FB post February 6, 2015.)  If he were firing at the limousine with his first shot, he could not have acquired the target as early as Z160 without drastically repositioning himself.  He could only have fired downrange from his position.  He *was* firing downrange, but not at the limousine and much earlier than Z160.

For reasons 1-7, see my blog post Thursday, May 21, 2015.

For the complete detailed analysis and supporting evidence, please see my book The Final Truth: Solving the Mystery of the JFK Assassination: http://www.thefinaltruth.net.