Kenneth O'Donnell, aide to President John F. Kennedy, stepped into a small cubicle at Parkland Hospital, where Vice President Lyndon Baines Johnson nervously waited with his wife and several aides to learn the condition of the president. Kennedy had been shot as his motorcade made its way through downtown Dallas on a sun-splashed November autumn afternoon.
"He's gone," O'Donnell said to Johnson, who through an assassin's hand had become the 36th president of the United States.
It was 1:30 p.m. Central Standard Time, Nov. 22, 1963.
"What was going through Lyndon Johnson's mind as he stood there, history will never know," writes Robert A. Caro in his recently published book, "The Years Of Lyndon Johnson: The Passage of Power," the fourth in his planned five-part biography of Johnson.
"The only thing that is clear is that if, during those long minutes of waiting, he was making decisions — this man with the instinct to decide, the will to decide — by the time O'Donnell spoke and the waiting was over, the decisions had been made," Caro writes.
The new president had made the decision that he was not going to leave Dallas without Kennedy's body and his widow, and the oath of office would be administered aboard Air Force One.
After leaving Parkland and speeding through Dallas streets, they arrived at Love Field, where they boarded the presidential plane.
Calls were made to Attorney General Robert F. Kennedy, the slain president's brother, regarding the wording of the presidential oath. It was eventually dictated to Johnson's secretary, Marie Fehmer, by Deputy Attorney General Nicholas Katzenbach, who died earlier this month at 90.
Katzenbach had advised that any federal judge could swear in Johnson, and Johnson knew which one he wanted.
"Get Sarah Hughes," Johnson ordered Fehmer.
As Hughes, a Baltimore native, sped to Love Field, the president's widow, still dressed in the pink blood-caked suit she had been wearing that day, calmly waited in the presidential stateroom as Lady Bird Johnson attempted to console her.
Johnson asked chief White House photographer Cecil Stoughton, "Where do you want us, Cecil?" as the photographer stood on a sofa to get a better vantage point to record the administering of the oath.
The cramped main cabin of the presidential plane, whose shades had been pulled down, was jammed with staff, aides and three reporters: Newsweek's Charles Roberts, Merriman Smith of United Press International and Sid Davis of Westinghouse Broadcasting Co.
In the background, Caro wrtes, was the moaning sound from a single engine that kept turning in order to keep essential functions aboard the plane in operation.
"Judge Hughes arrived, a tiny woman in a brown dress decorated with white polka dots, and Johnson showed her to the place Stoughton had selected, in front of the sofa on which the photographer was standing, and someone put a small Catholic missal in her hands," wrote Caro.
There were two witnesses Johnson wanted: Jacqueline Kennedy and Evelyn Lincoln, who had been JFK's secretary.
Johnson's hands were so large that when he laid it on the missal, he covered it, and then raised his right hand to repeat the presidential oath.
Once the oath was administered, Johnson lowered his hand and said, "Now let's get airborne."
"The whole thing took no more than 10 minutes," Hughes told The Sunday Sun Magazine in a 1972 interview. "I think as soon as I was off the steps, it took off."
Hughes was descended from the Tilghmans who settled in Maryland in 1660. One of her ancestors was Tench Tilghman, an aide to Gen. George Washington during the Revolutionary War.