Emerging from behind the Stemmons Freeway sign in the Zapruder film, the president is clutching at his throat as the First Lady turns toward him.  In the right frame(bottom) a dark-complected man, standing next to "Umbrella Man"(notice edge of umbrulla by the sign), raises a clenched fist in a seeming sort of gesture.  Could this have been an anti-Castro representative, reminding JFK right before his execution of the anti-Castroites unity in displeasure at his failure to provide air cover for the Bay of Pigs regiment that was soundly defeated by Castro?