Spain’s former king Juan Carlos has, for the first time, recounted how he accidentally killed his younger brother Alfonso nearly 70 years ago.

In his memoirs, published in France, Juan Carlos described the March 29, 1956 incident when, at age 18, he fired a .22-calibre pistol in a room at the family home in Estoril, Portugal, unaware a bullet remained in the chamber; the shot struck Alfonso, then 14, in the forehead, killing him in their father’s arms.

Juan Carlos called the tragedy a “before and after moment” in his life, leaving him with lasting grief and a sense of unhappiness.

No judicial inquiry was held at the time, and his father later disposed of the pistol in the sea, The Telegraph has reported.

The memoirs, written with journalist Laurence Debray, will be published in Spanish in December, while Juan Carlos, who abdicated in 2014 amid scandal, was not invited by King Felipe VI to the upcoming ceremonies marking the 50th anniversary of Franco’s death.