As of June 12, Queen Elizabeth II has been reigning for 63 years. She’s ruled through the administrations of 10 U.S. presidents, 12 British prime ministers, and countless world events.

But on June 13, 1981, it could have all been undone by a teenager. On that day, the Queen was riding her horse on her way to the annual Trooping the Colour ceremony when six shots rang out. She was unharmed, and though her horse was spooked, the sovereign was able to calm him and continue along the parade route.

Security rushed into the crowd to find the would-be assassin wearing a “Charles and Di” pin—and they were surprised to discover that he had fired six blank shots. Seventeen-year-old Marcus Sarjeant was obsessed with the assassination attempts on Ronald Reagan and Pope John Paul II, and idolized Lee Harvey Oswald and Mark David Chapman.

After the attempt on Reagan in March 1981, Sarjeant remarked that he wanted to be the first one to “have a pot-shot” at the Queen. Hoping to reach the same levels of fame as his idols, the teen wrote about his plans to “stun and mystify the world with nothing more than a gun” and even sent photos of himself posing with his father’s revolver to various media outlets prior to the attempt.

Fortunately, Sarjeant was unable to obtain ammunition in the U.K. Instead, he settled for the next best thing by carrying out what the judge later called “a fantasy assassination” via blanks. Sarjeant was sentenced to five years under the 1848 Treason Act, but was released in October 1984. After his time in a psychiatric prison, Sarjeant apparently changed his mind about wanting fame and notoriety. Upon his release, he changed his name, and, according to the BBC, started a new life.

A tourist was later looking through the photos he had taken and discovered that he had inadvertently snapped a chilling shot of Sarjeant taking aim. You can also watch the incident unfold in the video below.