James Tague was stuck in traffic in downtown Dallas around noon on November 22, 1963 when he became an eyewitness to history.

Then a 27-year-old car salesman, Tague was waiting for John F. Kennedy's motorcade to sweep by.

Riding in an open-top Lincoln Continental, the president, flanked by Secret Service bodyguards, waved to the lunchtime crowd, his wife Jacqueline at his side along with Texas Governor John Connally and his spouse.

"I noticed a car with flags on the front fender, coming through the crowd," Tague told AFP ahead of the 50th anniversary of Kennedy's assassination.

"That's where I remembered that I read about Kennedy being in town that day -- and then here comes a pop of a firecracker," he said.

"It turned out it's the first shot. Then there was a pause and then the crack-crack of two rifle shots."

On his right cheek, Tague felt something hit him -- a bullet that had ricocheted off the sidewalk, leaving him with a slight wound and no idea what just happened.

Within minutes, a deputy sheriff in plainclothes approached Tague and asked what was going on.

"I said I didn't know, but we noticed that a motorcycle had stopped over by the grassy knoll, and there's a couple of people talking to the motorcycle policeman," he said.

"We got there just in time to hear this man sobbing: 'His head exploded. His head exploded.' And the policeman said: 'Whose head?' And he says: 'The president's head.'"

By then the presidential motorcade had gone, racing the mortally wounded Kennedy to hospital.

Along with Connally, who was badly wounded, Tague was the only person injured on a fateful day that still weighs heavily on Americans' hearts and minds.

Pierce Allman, then 29, was program director at WFAA radio when curiosity drove him to go out to see Kennedy's motorcade go by the Texas School Book Depository on Elm Street.

"I was standing on the corner, across from the depository building and here came the motorcade. I waved and said: 'Welcome to Dallas, Mr President,'" he recalled.

Allman vividly remembers First Lady Jacqueline Kennedy in "that marvelous pink outfit," waving to the crowd, and Kennedy, "sort of waving" brushing the hair off his face.

Then came the "boom" that Allman says he'll recognize "for the rest of my life."

"But it didn't go through my mind (that) this first attempt was a shot. It was not the flat-cracked sound of a rifle. It was a loud boom sound. It came from in front and directly above," he said.

"I thought at first, well, it's a firecracker ... and then boom! Second shot...

"During the first shot I had looked up and on the fifth floor (of the depository) there were three guys hanging out of the fifth-floor window and looking up at the sixth floor.

"I looked up at the sixth floor but things were happening so fast I couldn't tell you if I saw a rifle-bearer or not."

On the second shot, Allman saw Kennedy's hands go up to his neck, and heard Mrs Kennedy screaming.

Then came a third shot, and "Kennedy did a violent sideways move."

Hugh Aynesworth, "a little put out" for not being assigned to cover Kennedy's visit by his newspaper, the Dallas Morning News, where he was a 32-year-old science and aerospace editor, ventured down to Dealey Plaza on his own because "you don't see a president every day."

"The crowd along Main was very heavy, very excited. I couldn't get closer so I kept walking, so that's why I ended up over here" at Dealey Plaza, he said.

"As they passed me, Jackie was so happy she was beaming, Kennedy was waving -- and all of a sudden, I heard what I thought was a motorcycle backfire, but it wasn't a motorcycle," he said.

"I can tell the next two were shots from a rifle. I saw people immediately grabbing each other -- some running each direction, some falling down, covering their kids, screaming, crying. It was a mass hysteria within seconds."

Phyllis Hall, a 28-year-old nurse at Parkland hospital, was starting her lunch break when her supervisor cryptically announced that there had been "an accident" in Kennedy's motorcade.

"The doors from the outside just blew open," she recalled.

"There was a lot of chaos and shouting. Here came a cart with the governor Connally -- he was very gravely injured -- and (then) came the next carriage.

"I would learn a few minutes later this is the one that had the president on it."

Hall worked in the emergency ward four years previously, so when a "gentleman carrying a very big gun" took her by the elbow and said "we need you back here," she did not resist.

"When we got into Trauma Room One, Mrs Kennedy was standing at the foot of the cart," she said.

"In my estimation, the president was dead on arrival because he was very grayish-blue. He was especially dark blue around his mouth. I felt for vital signs. There were none. I saw no movement.

"The other doctors came down. They started to do a tracheotomy... There was nothing to do because just before we stopped the emergency measures, a doctor, a neurosurgeon came down, he came over...

"He lifted up the piece of hair (from Kennedy's head) and that's where I could see that a great amount of brain matter was no longer in the head. It was all over Jackie. It was on the Connallys and I'm told it was all over the cart."

President John F. Kennedy, admitted to Parkland hospital at 12:38 p.m. as patient number 24740, was declared dead at 1:00 p.m.