It took eight minutes for President John F. Kennedy to arrive at Dallas' Parkland Memorial Hospital after being fatally shot in Dealey Plaza on Nov. 22, 1963.
Doctors and nurses poured into Trauma Room One desperate to save the president's life.
Dr. Robert McClelland was in an upstairs room with hospital residents, watching a video, when he got a knock on the door.
"They just called from the emergency room and said the president's been shot. They need everybody downstairs," he recalled.
McClelland will never forget the crush of people in the operating room area. Doctors, nurses, agents with the Federal Bureau of Investigation and Secret Service all poured into the room.
"It was jammed with men in business suits, shoulder to shoulder. You couldn't pack one more man in that area," he said.
As nurses worked to clear the operating room of onlookers, McClelland stood at the head of the gurney, holding a metal retractor to Kennedy's small throat wound.
He was looking straight down at a gaping hole in the president's head.
"I could see that the whole back half of his right cerebral hemisphere was gone," he said.
McClelland was about 18 inches from Kennedy's head.
"I was horrified to see him like that. With his head covered in blood, with that light shining down on it."
NBC 5 asked McClelland how large the hole was in the back of Kennedy's head, he made a circle with his hands about the size of an orange.
"It was a hole about like this size. As I said, the whole back half, the right side of his brain was gone," he said.
Even today's medical advances couldn't have saved the president. Within 10 minutes, a priest came to deliver the last rites.
Most of the doctors cleared the room. But McClelland found himself trapped behind a gurney pressed against the wall and couldn't get out before the priest arrived.
"It was a private moment, and I'm a bit embarrassed that I was there. But I didn't want to have to walk across the room past the priest," McClelland said.
NBC 5 asked McClelland to remember what the priest -- Father Oscar L. Huber -- said during the ritual.
"Before he said anything he made the sign of the cross on the president's forehead, anointed his forehead. And then he leaned over and said, 'if thou livest,' in a loud, audible voice. Then he completed the rest of the ceremony in a softer voice and I couldn't hear him."
Jackie Kennedy then walked into Trauma Room One, her pink suit covered in her husband's blood. The first lady spent a few, final moments with her husband.
"She stood there for a minute over him. And then she exchanged a ring from her finger to the president's finger," McClelland remembers.
"And she stood there another moment or two, and then walked slowly to the end of the gurney, where the president's right bare foot was protruding out from underneath the sheet that was covering him. She stood by his foot for a moment, leaned over and kissed his foot, and walked out of the room. And that was the last I saw of the first lady."
"It was a very significant, emotional, and heartbreaking moment, I would say," McClelland softly said.
He said Jackie Kennedy did not weep, but "was very self-contained and calm."
The only time she choked up, he remembers, was when Huber told her husband had been granted "conditional absolution. I could tell she didn't like hearing those words."
The men who operated on Kennedy were not wearing surgical scrubs. It was lunchtime, and most of the doctors were either out at lunch or teaching classes to residents. They were in business suits.
McClelland had his bloody suit dry cleaned the next day, over the dry cleaner's protest.
"This suit is a part of history," the dry cleaner said. “You should save it.”
McClelland looked at his wife. "My husband only has one other suit," she interjected.
But McClelland didn't get his bloody dress shirt dry cleaned. He's kept it all these years, usually tucked away in a box at home or in his briefcase. It's a memento, a small piece of history from one of the darkest days in American history.
The front of the shirt is still stained with Kennedy's blood.
"I can still visualize that to this day in my mind, as well as the day I wore it," he said. "Things like that are burned into your memory. That's Kennedy's blood. And I was soaked in it."
Some day, McClelland said he'll donate the 50-year-old shirt to the Sixth Floor Museum, which is housed in the Dallas building that was once the Texas School Book Depository -- the same building from where Lee Harvey Oswald is believed to have fired the shots that killed the president.
It will be a final bit of closure for McClelland's long and storied career as a surgeon at Parkland Hospital. A career forever marked by his desperate efforts to save a president's life.