Dallas motorcycle officer Marion L. Baker and TSBD Superintendant Roy S. Truly met a man on the 2nd floor of the Texas School Book Depository about 75-90 seconds after the shooting in Dealey Plaza.
(The assassination of President John F. Kennedy, Dallas, Texas, November 22, 1963)
Part 2: http://youtu.be/IkQWc6yARRs
Part 3: http://youtu.be/ZfIwO9uJfio