word trickled into that plane and you can imagine that day they had flown into dallas and they had watched their president leave in a limousine and now they're hearing over radios that he's gone. >> he's listening to charlie frequency on the radio surroundeded by $2 million of the highest tech communication gear on the planet. explain what he hears and what starts to happen. >> he can hear the secret service agents so he can hear the motorcade as it winds its way through dallas. what he immediately hears is the secret service agents saying to cover johnson. everyone has code names. all of the secret service agents have code names. johnson's code name was volunteer. he hears cover volunteer. he doesn't know why. he thinks at that moment that john f. kennedy's back had gone out and that the motorcade had to stop