A Trooping the Colour ceremony from 1981 turned out to be one of the most alarming incidents for the British police after a 17-year-old man fired six shots at Queen Elizabeth in close range.

According to People, Marcus Sarjeant attacked the Queen as she was leading her troops on her horse during the ceremonial procession. Guards immediately wrestled and pinned the teenager to the ground and they discovered that his gun had blank bullets. 

Witness Alec Galloway, who was one of the guards who tacked Sarjeant, said that Queen Elizabeth appeared "shaken" by what happened but she regained her composure right away. She, then, gave her beloved Burmese horse a pat, to calm the animal down, and then rode off the scene as if nothing serious happened.

In a BBC documentary in 2016, Prince Charles recalled how his mother handled the horse, whom she kept patting to reassure the animal. The Prince of Wales also said that the Queen is "made of strong stuff."

On Sept. 14, 1981, or three months after his attack, Sarjeant was sentenced to five years in prison. The teenager was charged under the 1848 Treason Act. 

While imprisoned, Sarjeant allegedly sent letters to Queen Elizabeth but did not receive a reply from the monarch. In his diaries, the teenager wrote that he wants to be "the most famous teenager in the world" and was obsessed with U.S. presidents and the deaths of John Lennon and President John F. Kennedy.

Sarjeant, who was tried to sign up for the Royal Marines and the Royal Army, also sent Queen Elizabeth letters before the Trooping the Colour. He warned her not to go out because she will be assassinated but his letters were reportedly received at Buckingham Palace days after the annual summer event. 

Ultimately, Sarjeant served prison time for three years out of his five-year sentence in a psychiatric facility. He was mostly isolated from the other inmates as the other prisoners apparently didn't treat him right for what he did to the Queen. Today, Sarjeant reportedly has a new name and a new life, per BBC.

This attempted assassination will likely figure in the upcoming season 4 of Netflix's The Crown. The teaser shows Queen Elizabeth at the Trooping the Colour. Producers have hinted that this new season will open in the late '70s and will mostly feature the royal events of the 1980s, including Prince Charles and Princess Diana's monumental wedding.