On CBS Radio, when the UPI bulletin comes in, Alan Jackson seems to heave a big sigh, then reads the text with the preamble, "Ladies and gentlemen, the president is dead." He finishes the flash, there's a pause, then someone tries to roll some music, playing at the wrong speed. He is also the one who pauses, then skips over the earlier wire service report that Cllint Hill said to Scotty Reston, "He's dead."
On ABC, stalwart Don Gardner reads the flash, says, "Let us pray," silent pause (which sounds edited in on the version I've heard), then turns it over to Quincy Howe for comparison to other assassinations.
NBC Radio had Edwin Newman reading takes as they were fed to him. He gets the one about the "two priests who were with President Kennedy say he is dead," drop his voice in volume and says, "I will repeat that, with the deepest regret, two priests who were with President Kennedy say that he is dead." (Emphasis mine. Does anyone remember if they were carrying TV audio at the time the official announcement is made?
And which network (I think NBC-TV) that reported the first official White House confirmation of the death was a shot of the flag being lowered to hast-staff.