The Longest Day had begun.

The street curved as we passed by an undistinguished building later described to me as the Texas School Book Depository. We were on Dealey Plaza. Suddenly, the car in front of us accelerated from 8 miles an hour to 80. I saw a policeman wildly waving us ahead, and buildings began to blur as we raced to keep up. Then we lost the car in front of us as we swerved to avoid people running across our path.

The whole spectacle turned bizarre as we drove madly toward or away from some unnamed terror. What had happened? As if unwilling to know the answers, I found myself saying to our driver, “I think the president is late to his speech at the Dallas Trade Mart. Let’s get over there as quickly as we can.”

We caromed through the streets and wound up at the Trade Mart. We drove to the back entrance to make inquiries. Surely someone could confirm what we eagerly wanted to hear, that the president had been a bit delayed by some security precautions but would soon make his speech.

At the entrance, a distraught-looking man raced past us, his coat and tie flying, to a pay phone down the hall. He was holding a transistor radio, and through the crackle of static we could hear the announcer’s voice: “The president and the governor have been shot … Parkland hospital!” I yelled at a man standing next to a dusty Chevrolet. He looked up, startled. I grabbed him by the arm and said, “I have President Kennedy’s secretary with me. Can you take us to Parkland hospital right now?”

He was a deputy sheriff, and he would take us. We raced to Parkland, siren screaming. When we arrived at the hospital, its entrance was cluttered with cars parked helter-skelter and blocked by a swarm of uniformed police and plainclothesmen. I ran down the hall and down the steps to the basement, where I had been told the vice president could be found. The basement was a mass of people, their stunned faces a collage of anxiety and grief.

Congressman Homer Thornberry was going to visit Nellie Connally [the wife of Texas governor John Connally], so I joined him. She sat in a small room, her eyes red, her hands in her lap, her face drawn and pale with anxiety. Lady Bird Johnson sat beside her.

“How is John?” I asked.

She looked up, tears filling her eyes. “We don’t know. We just don’t know.” Mrs. Johnson embraced her.

I wandered out into the hall again. As I entered the stairwell to walk upstairs, I bumped into Cliff Carter, one of LBJ’s aides.

“The vice president wants you, and he wants you now.” Cliff pulled at my arm, then he stopped and said softly, “The president is dead, you know.”

I didn’t know. Tears overcame me, and try as I might, I couldn’t regain my self-control. Cliff stood silently for a few seconds, and then very gently he said, “We must go now, Jack. The vice president is waiting for us. Compose yourself.” I murmured something, wiped my eyes, and together we set off to find Lyndon Johnson.

A few moments later, we were in a small room on the basement floor. It was empty except for a Secret Service agent standing by the door. He was Lem Johns, later to become a trusted member of the White House Secret Service detail. Johns had clearly been waiting for us. “I’m to take both of you to Love Field. Mr. Valenti, the vice president wants you aboard Air Force One right now.”

Johns piled us into a police car, and with siren keening, we sped toward Love Field. I was puzzled. Why was I going to Air Force One? I needed to get back home to Houston. My thoughts were tumbling inside me, and I could barely make sense of them.

When we got to the airport, Air Force One had been moved to a remote corner of the field and was being guarded by a cordon of menacing, heavily armed men, their Uzi-type machine pistols at the ready. I clambered aboard the presidential plane, acutely aware of my own apprehension. This was new, unexplored territory. I had no idea what was in store for me.

The plane was thickly packed with somber-faced officials and others, and I looked up as the huge figure of Lyndon Baines Johnson suddenly emerged. His face was grim, but beyond that he betrayed no emotion. Everyone seated rose respectfully.

He saw me and beckoned. I went quickly to his side. He murmured to me in a soft voice, “I want you on my staff. You’ll fly back with me to Washington.” That was it. Within seconds I became the first newly hired special assistant to the president.

Then I blurted out two questions that even now cause me to wince in embarrassment. “But, Mr. President,” I said chokingly, “I don’t have any clothes.”

LBJ looked at me as if wondering, “Who is this cretin I am bringing to my staff?”

“Well,” he said, “we have phones on this plane. Call your wife and have her send some to you. Or you can buy whatever you need in Washington.”

Then I hurled another one at him: “But I don’t have a place to live.”

His answer was swift and decisive: “You can live with me until your family gets to Washington.” And that was precisely what I did. I took up residence at the Johnsons’ Spring Valley home for eleven days, until they moved into the White House.

The president then turned his attention to more-pressing business. He was on the phone with Rose Kennedy, the mother of JFK. He spoke softly to her: “Mrs. Kennedy, I wish to God there was something I could do for you.” He listened for a moment and then said, “Please, Lady Bird wants to talk with you,” and he passed the phone to Mrs. Johnson.

After that conversation ended, LBJ then called Nellie Connally, and he and Lady Bird chatted with her, their concern obvious. He then called McGeorge Bundy, the national security adviser, and his own most trusted aide, Walter Jenkins. Bundy and Jenkins received their instructions: “Reschedule the Cabinet meeting for Saturday. Get hold of the congressional leaders. Tell them I want to meet with them as soon as I get to the White House.”

The president spoke several times with Secretary of Defense Robert McNamara, with deputy attorney general Nicholas Katzenbach, and finally with Bobby Kennedy. While the rest of us on the plane were in varying degrees of hysteria, LBJ was preternaturally calm. Faced with the gravest challenge to America in that century, he had exercised phenomenal control over his galvanic moods.

There were two pressing questions. First, should we get airborne or wait for the body of the late president to be brought aboard? The Justice Department was urging swift departure, as was the Defense Department. Without hesitation, LBJ said flatly he would not depart Dallas until the coffin was secure on the plane. He understood intuitively that he could not leave the body of President Kennedy alone in Dallas.

The other question was harder to answer. When should the new president be sworn in? McNamara and Katzenbach both recommended that the president hold off. “It’s a formality, Mr. President,” said Katzenbach. “You can be sworn in later.” Secretary McNamara told Johnson that fighter planes had been scrambled from Barksdale Field, in Shreveport, and Bergstrom Field, in Austin, to escort Air Force One back to Washington. No one knew the extent of the danger posed by Kennedy’s squalid assassination.

Johnson didn’t question the logic put forward by McNamara and Katzenbach. He was simply seeing clearly what others didn’t. The swearing-in ceremony wasn’t essential to grant him presidential authority, but he saw that the entire world, not just the United States, was in a state of shock. LBJ judged it crucially important that he try to stanch the flow of fear before it spread too far too fast. Though I did not know it, LBJ had already summoned Judge Sarah T. Hughes, whom he had suggested that President Kennedy appoint to the federal bench, to swear him in as president.

What Johnson had also chosen to do was have his swearing-in photographed and to have that film developed as soon as the presidential plane landed at Andrews Air Force Base. The photos would be flashed immediately to every country on earth. He meant to impress on this anxiety-ridden world that in the United States, the Constitution endured. For what the Constitution declares is “The president is dead. The president lives. The nation goes on.”

My first official duty aboard Air Force One was to phone Katzenbach, whom I had never met. I identified myself and said, “Mr. Katzenbach, we’re in rather urgent need of the exact wording of the official oath of office. If you can dictate it to me, we’ll type it up for use by Judge Hughes.”

There was a moment’s hesitation on the other end of the line. “Of course. Let me find it, and I’ll get right back to you.”

What I learned later was that Katzenbach, brilliant lawyer that he was, didn’t know where to find the oath. I sure as hell didn’t know. Some minutes later, he called back. “We have the oath. If you’ll get someone on the line to take it down, I’m ready,” he said.

“Fine,” I said, “but can you tell me where you found it?”

I could almost hear Katzenbach smiling. “In the Constitution.”

Of course.

Within seconds, Marie Fehmer, LBJ’s unflappable and superbly efficient secretary, had the presidential oath of office typed cleanly on white paper and ready for Judge Hughes. We looked around for a Bible. None was to be found, but we did locate a Catholic missal in the presidential bedroom.

Judge Hughes was now aboard the plane. LBJ asked one of the Kennedy aides if  Mrs. Kennedy would feel comfortable coming forward to stand next to him as he took the oath of office. She agreed to do so. I saw her emerge slowly from the rear of the plane, walking as if in a trance. Her pink blouse was liberally spotted with her husband’s blood, as well as fragments of his brain matter that had sprayed her when the assassin’s bullet struck, but she had refused to change into another garment. While I marveled at her strength, she came to a stop at LBJ’s side. Her eyes were open but unseeing. I had read and heard of catatonic trances, but I had never confronted one until Mrs. Kennedy came forward to stand next to President Johnson.

The picture recorded by Army captain Cecil Stoughton’s camera is arguably the most famous photograph of the twentieth century. There it is, in black and white: LBJ, his right hand raised, with the top of Judge Hughes’s head in the foreground, along with Mac Kilduff, JFK’s assistant press secretary, holding a live mike. To Johnson’s left is Mrs. Kennedy, and to his right stands his wife, Lady Bird. Next to her is the tall figure of the late congressman Albert Thomas. It was Thomas who pulled me from my position behind him to his side for a better view of the most dramatic swearing-in of a president in the history of the nation, saying, “Come around here, Jackson, you have to see this up close.” I had no idea that as a result, my face would be frozen forever in that famous photograph, but there I was in the lower left-hand corner of that picture, my face distraught, incomprehension in my eyes as I stared at Lyndon Johnson.

Once Air Force One had lifted off and Mrs. Kennedy had retired to the rear of the plane, the new president roamed the aircraft. At one point, he motioned me to sit beside him, with aides Bill Moyers and Liz Carpenter in the facing seats. LBJ asked a steward for a glass of water. Why do I remember this? Because when the steward returned, LBJ reached past me to take the glass. His huge fingers were literally inches from my eyes. What I saw was astounding. The president’s hand was absolutely steady. “How could that be?” I thought. Later on as I got to know LBJ intimately, I recalled a line Winston Churchill had written about Henry II of England: “It was said that he was always gentle and calm in times of urgent peril, but became bad-tempered and capricious when the pressure relaxed.”

Then the president said, “I want you [meaning Moyers, Carpenter, and me] to put something down for me to say when we land at Andrews. Make it brief. We’ll have plenty of time later to say more.” When the president rose, the three of us began trying to create the statement he wanted. Finally, we reached a consensus. It certainly was short: 58 words, to be precise. The president read over our draft once, then twice. He nodded, took out a pencil, and changed one line. Where we had crafted the last sentence to read “I ask for God’s help and yours,” he switched the emphasis: “I ask for your help and God’s.”

Not long afterward, Air Force One touched down. LBJ and Mrs. Johnson stepped onto the brightly lit tarmac, and the air was chilly as they approached the cluster of microphones around a temporary lectern. Television lights stabbed the darkness. It was 6:10 p.m. eastern standard time when the president, his face somber, began his statement: “This is a sad time for all people. We have suffered a loss that cannot be weighed. For me it is a deep personal tragedy. I know that the world shares the sorrow that Mrs. Kennedy and her family bear. I will do my best. That is all I can do. I ask for your help and God’s.”

Once his brief speech was done, the president headed for the two helicopters sitting ready on the tarmac. He beckoned to me, and I climbed in after him, joining the Secret Service agents and others already onboard. We took off and several minutes later landed softly on the South Lawn of the White House. It was my first visit, and I had as my tour guide the new president of the United States.

We went inside the Diplomatic Reception Room, then walked through the basement to the portico of the West Wing. The president did not enter the Oval Office. Instead we strode across West Executive Avenue, a guarded private street for the use of government officials and special guests of the White House. We entered the Executive Office Building and took the elevator to LBJ’s vice presidential suite of offices on the second floor.

McGeorge Bundy was waiting in the LBJ offices when we arrived. Bundy briefed him on all matters that demanded swift response. Averell Harriman, then undersecretary of state for political affairs, and Senator Bill Fulbright, the chairman of the Senate Foreign Relations Committee, were ushered in. The moment Harriman and Fulbright departed, the president got on the phone, calling first President Truman, then President Eisenhower, and then Sargent Shriver, brother-in-law to President Kennedy.

At 9:25 p.m., after various meetings and phone calls, President Johnson asked Bill Moyers, Cliff Carter, and me to join him in his limo, headed for his Spring Valley residence. There Rufus Youngblood, head of the new Secret Service detail, met us in the driveway. “Mr. President,” said Rufus, “we haven’t had time to put in secure phones yet. So just remember when you talk, you’re on AT&T. No security.” The president nodded and even managed a smile.

When we all got inside, LBJ greeted and talked with several dozen close friends and colleagues who were already there. He sipped orange juice. Finally, as midnight neared, he prepared to go upstairs. He nodded to Bill, Cliff, and me, and we followed him to the second-floor master bedroom. He had now been president for a little more than eleven hours.

Mrs. Johnson had apparently gone to another bedroom, leaving LBJ with the three of us. He changed into pajamas and sat upright in his large bed, his back leaning against the headboard. We watched the television set with morbid fascination.

We stared at the glowing screen while LBJ began to ruminate. “I’m going to pass that civil rights bill that’s been tied up too damn long in the Senate. I’m going to get that bill passed by Congress, and I’m gonna do it before next year is done. And then I’m going to get a bill through that’s gonna make sure that everybody has a right to vote. You give people a vote, and they damn sure have power to change their life for the better.”

Later on, he pointed to the TV set when the commentator made some remark about Harry Truman. “By God, I intend to pass Harry Truman’s medical insurance bill. Never again will a little old lady who’s sick as a dog be turned away from a hospital because she doesn’t have any money to pay for her treatment. It’s a damn disgrace.”

And he wasn’t through yet. As we watched the TV screen, he spoke up again, forcefully: “We are going to do something about education. We’re going to pass a bill that will give every young boy and girl in this country, no matter who they are, the right to get all the education they can take. And the government is going to pay for it.” I was beginning to feel like an intimate observer to an unprecedented historic moment.

Finally, sometime between 3:30 and 4:00 a.m., President Lyndon Johnson suggested that we try to get some rest. Strange, but even after the day’s terrible events, and after going without sleep for almost 24 hours, I wasn’t tired. As I lay and turned on a bed belonging to Lynda Bird, I knew I would never forget a moment of that day. And I wondered if the man who lay not thirty feet from me, the new president in the next room, would sleep at all.

The Longest Day was over.