A US Secret Service agent who leapt onto John F Kennedy's limousine as it came under fire in Dallas, and was pictured in famous photos of one of the most dramatic events in US history, has died at the age of 93.

Clint Hill later became a bestselling author but was haunted for decades by guilt over Kennedy's assassination.

Hill died at his home in California on Friday, according to a statement from his publicist.

On 22 November 1963, he was assigned to protect the president's wife, Jacqueline Kennedy.

Hill was riding in a car behind the Kennedy limousine when the first shot rang out.

He immediately rushed towards the couple and started to climb onto the back of the limousine as the shooting continued.

Hill's actions during the assassination were captured on the Zapruder film – an amateur home video that provided one of the best recordings of the shooting.

Hill, originally from North Dakota, served in the Army prior to joining the Secret Service in 1958.

He was given an award for his actions in Dallas and eventually rose to become assistant director of the Secret Service.

However the trauma he experienced during the assassination led him to retire early from the agency in 1975, at the age of 43.

He had become convinced that he could have saved Kennedy's life and shortly after his retirement told CBS 60 Minutes that he felt responsible.

"If I had reacted about five-tenths of a second faster, maybe a second faster, I wouldn't be here today," Hill said.

"You mean you would have gotten there and you would have taken the shot?" asked interviewer Mike Wallace.

"Yes, sir... That would have been fine with me," Hill responded.

"I have a great deal of guilt about that," he said. "Had I turned in a different direction, I'd have made it. It's my fault."

As the years went by, the former Secret Service agent later told a documentary, he returned to Dallas, eventually coming to the conclusion he could not have saved Kennedy's life.

Hill met journalist Lisa McCubbin in 2009 and collaborated on a bestselling memoir, Mrs Kennedy and Me.

It was the first of a series of books and Hill and McCubbin fell in love. The couple married in 2021.

A statement from his publisher said that Hill had died at home with his wife at his side. A cause of death was not given.