That would be Bobby Hargis, who reacted quickly and quite
professionally to the shooting, first running up the (not yet famous)
grassy knoll, then, not finding anything suspicious there, heading
back to the area of the Book Depository. His testimony has been used
to support theories of a grassy knoll gunman, although he himself has
never promoted such theories. John McAdams wrote this article about
it:
http://mcadams.posc.mu.edu/hargis.htm
Dave