His dark hair has long since turned white. The years have accentuated his features, and sunken eyes surrounded by deep, dark circles betray a lifelong anguish.
A dozen years after Kennedy was killed, Hill expressed his guilt in a brutal, emotional 1975 interview with Mike Wallace on 60 Minutes for not climbing aboard the president's limousine more quickly to shield him from the fatal shot.
"Had I turned in a different direction, I'd have made it," said Hill, who had just retired for health reasons at age 43. "It's my fault. ... And I'll live with that to my grave."
He subsequently withstood many difficult years, including bouts with alcoholism and pills, before taking hold of his life. After two trips to Dallas – with his wife in 1990 and fellow former agents last June – and spending hours in Dealey Plaza, Hill no longer feels that way.
"I came to the conclusion that I did the best I could and there was nothing more I could have done that day," he said during a panel last week at Georgetown University that previewed The Kennedy Detail, a book and television documentary in which Hill joins other members of Kennedy's protective detail in telling their version of that day's events.
On Saturday, Hill, former agent Jerry Blaine and author Lisa McCubbin will reprise that preview at The Sixth Floor Museum in downtown Dallas. On Monday, the documentary will air on the Discovery Channel on the anniversary of Kennedy's death.
They're speaking out now, Blaine said, to counter the increasing belief that Lee Harvey Oswald was part of a larger conspiracy when he killed Kennedy.
"Over 47 years, there has not been a single bit of evidence to show that it was a conspiracy," said Blaine, who helped advance Kennedy's ill-fated Texas visit. "If we don't speak up and put a balance to this, history would never know exactly what happened."
The book contains previously unpublished nuggets, such as the incident at 2:15 the next morning when Blaine, on duty at Lyndon Johnson's Washington home, thought he heard an intruder and found himself pointing a loaded submachine gun at the new president.
But the heart of the story is their detailed description of one day in Dallas.
As Kennedy's car crept through downtown's crowded streets, Hill scanned the crowd from the running board of the follow-up car; Kennedy had barred agents from the back of his limousine. Suddenly, Hill heard "a loud, explosive noise to my right rear." He jumped down and ran toward Kennedy's moving car, never hearing Oswald's second shot.
"When I got to the president's vehicle, just as I approached it, the third shot rang out, hitting the president in the head, just above the right ear," he said. "It left a hole about the size of my palm."
He climbed aboard the trunk, pushing Jacqueline Kennedy onto the seat. Seeing the extent of the president's wounds, he signaled thumbs-down to the follow-up car "so that they knew the situation was dire."
At Parkland Hospital, the first lady initially refused to leave the limousine until Hill covered Kennedy's comatose body and bloody head with his jacket.
Though many details had been told before, the story remains riveting, especially for those of us who vividly remember that day.
The situation an inadequately staffed Secret Service faced in Dallas, Blaine notes, was one Kennedy himself once cited as when he'd be most vulnerable. "The one thing we always feared was somebody in a window hidden away with a rifle, which is what happened," he said.
For years, the agents never discussed the assassination among themselves. But after reconnecting at a 1990 San Antonio meeting, Hill returned to Dallas, where he says in the book he first "realized that, even had he been on the back of the president's limousine, Oswald would have hit the president."
It remains one of our era's seminal moments. "Everything changed," Hill noted last week. "The age of innocence just died right there."