With 45 years of practice, Bill Newman repeats what he saw on Nov. 22, 1963, dispassionately and in quick order.
After witnessing President John F. Kennedy's arrival at Dallas Love Field, he pressed the speed limit along Cedar Springs Road to get his family to the parade route along Dealey Plaza. They arrived about five minutes ahead of the motorcade.
As the presidential limousine approached, he heard a sound that he assumed was a firecracker, and then another. The president briefly raised his arms and then gazed out at the crowd with a bewildered look. A third shot. The president slumped into his wife's lap.
Mr. Newman and his wife, Gayle, pressed their children to the ground along the grassy knoll and, in a moment caught by photographs beamed around the world, shielded them with their bodies.
As a living eyewitness to the JFK drama, Mr. Newman, 67, is a member of an ever-more exclusive club.
Gary Mack, curator of The Sixth Floor Museum at Dealey Plaza, estimates that of the several hundred people on the scene that day, less than half - and perhaps only a quarter - survive today.
Mr. Newman, beginning minutes after the presidential assassination and as recently as this week - at a program at The Sixth Floor Museum - has endlessly recounted the story to reporters, law-enforcement officials, historians, conspiracy theorists, friends, family members and inquisitive strangers.
The retired electrician, who now lives in Sachse, considers the decades of answering inquiries a privilege and a burden.
"I feel a little responsibility. I feel a certain obligation because it was my little part of a bit of history," he said. "But it was not a highlight of my life."
Time has taken an accelerating toll on participants who had a role - large or small - in that weekend's drama.
Nellie Connally, the former Texas first lady who was the last surviving occupant of the presidential limousine, died in 2006. Lady Bird Johnson, who was riding in the car just behind, died a year later.
Joe R. Cody, the Dallas police officer who bought the handgun that nightclub owner Jack Ruby used to kill Lee Harvey Oswald, died this past June. Paul Bentley, the detective who dived across a row of seats at the Texas Theatre to subdue Oswald, died in July.
Fay Puckett, whose mother rented a room to Oswald at her Oak Cliff rooming house, died in September. Cecil Stoughton, the official White House photographer who captured the image of Lyndon Johnson taking the oath of office aboard Air Force One, died this month.
"We're becoming extinct," said Ernest Brandt, 82, one of the eyewitnesses at Dealey Plaza that day. "I don't know how many of us will be around for the 50th" anniversary.
The presidential murder has been so thoroughly investigated, and the witnesses so often interviewed, that their diminishing ranks won't affect the narrative of that weekend in Dallas, said Vincent Bugliosi, author of the exhaustive Reclaiming History: The Assassinationof President John F. Kennedy.
"If there's any other witness out there and they haven't told the story by now, you can be 99.99 percent sure they don't have anything new to say," said Mr. Bugliosi, who lives in Los Angeles.
If anything, time only adds to the confusion, he said
"A lot of people have told the same story for the 10th time, and their recollections become fuzzier as time goes on," he said. "They hear other people saying things, and a lot of times it alters their memory of what they really saw."
But Mr. Mack believes the death of each player or eyewitness represents a loss to historians.
"The people with firsthand knowledge of the events of that day provide a richness of detail that can't be found in any of the FBI or Dallas police reports," he said. "The reports can say what people saw, but not what they felt. It's called context."
The eyewitnesses still provide details that, though historically insignificant, lend history a human dimension.
The Newmans were perhaps the closest parade spectators to the presidential limousine at the time of the shooting. Mrs. Newman recalled how she intended to take the family's movie camera to film the motorcade. If she had, it might have provided an even clearer view of the murder than the famous Zapruder film. But it was not to be.
"I can't tell you why, but we left it sitting in a drawer with the film inside it," she said earlier this week. "It's probably still sitting there to this day."
Nonetheless, her brush with history has given Mrs. Newman, 67, opportunities not often offered to the wife of an electrician. When the 1991 movie JFK was being filmed in Dallas, she was introduced to its star.
"She got to meet Kevin Costner," her husband recalled with a chuckle. "She says it was one of the greatest thrills of her life, something that I don't understand."
The couple has learned to be wary of being interviewed by researchers with preconceived theories, but decades of experience have given Mrs. Newman the confidence to shed her fear of being publicly quoted.
"I learned no one is going to get you for just talking," she said.
Richard Trask, a Danvers, Mass., archivist who compiled a book of photographs taken by assassination witnesses, has watched in dismay as so many have died over the years.
The toll reduces living memory to dry print, he said.
"It was an event that became a whodunit, and now it's in the realm of history," he said. "As more people die off, it becomes less a part of people's lives."