SAN FRANCISCO (CBS SF) -- It's been 56 years since President John F. Kennedy was assassinated and sent a nation into mourning, and not a day goes by that former Secret Service agent Clint Hill doesn't think about it.
Over the course of the 87-year-old's extraordinary career, Hill served five presidents, including Dwight Eisenhower, Kennedy, Lyndon Johnson, Richard Nixon and Gerald Ford.
"I've been around world leaders from kings, to the popes, queens and the presidents," said Hill. "It's amazing."
But it's his time with the Kennedys that forever changed him. Hill was assigned to first lady Jacqueline Kennedy after the 1960 election and he wasn't too thrilled.
"I wanted to be where the action was and that was with the president," Hill said.
But he soon realized Mrs. Kennedy was different.
"She was very active, athletic, and very smart," Hill said. "She spoke French, Italian, Spanish and we traveled the world. So I really had the best job of all the agents beginning in 1961."
Everything was good until August 1963 when the Kennedys' son, Patrick, died two days after birth.
"She was just destroyed," Hill said. "She was so depressed."
And just three months later Mrs. Kennedy would be devastated again
The couple traveled to Dallas on November 22, 1963. Hill was advised that a flyer was being passed around with the president's picture on a wanted poster.
They didn't know what to expect but the crowd was welcoming and rapidly grew.
"When we got to Main Street the crowds were so large they couldn't be contained on the sidewalk," Hill said.
He was on a running board on the car behind the president and first lady's vehicle when Hill heard the first gunshot. He realized President Kennedy had been hit.
Three shots total were fired.
"So about that time Mrs. Kennedy got up on the trunk. She came out of the back seat," Hill said. "She was trying to grab some of that material that came out of the president's head. And she did get a hold of some of it. I grabbed her and I put her in the backseat"
"I got on top of the car and laid up on both of them up in the back of the trunk and I looked down," he continued.
What he saw confirmed the worst. Soon after arriving at the hospital, Hill was on the phone with Attorney General Robert Kennedy.
"He said 'Well, how bad is it?' and I didn't want to tell him that his brother was dead," Hill said. "So I said, It's as bad as it can get and with that he just hung up the phone."
Clint stayed on as Mrs. Kennedy's detail for a year after the assassination but it was tough for him.
"Watching those two kids without a father now knowing that we were supposed to keep their father alive and we didn't do it," Hill said. "It just ate me up."
Hill never really talked about that day and fell into a depression and drinking after he retired in 1975. He eventually pulled himself out of it realizing what that day in November did to him.
It wasn't until 2009 when he met Lisa McCubbin who was writing a book about President Kennedy. He started to open up and started to heal.
"When I first met him his head was down," said McCubbin. "When he walked he was always looking down. And he just started standing up straighter, that confidence returned."
Hill and McCubbin would write three books together about his time as a Secret Service agent. She convinced him to move to Marin in 2012 and he's been there ever since.
Life is good but when November 22nd comes around, it's a time for Hill to reflect.
"It changed everything," Hill said. "I call it the end of the age of innocence."
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