Britain’s Prince Harry revealed in an upcoming book of his memoirs that he killed 25 people as an Apache helicopter pilot during his second tour in Afghanistan.

Prince Harry’s claim in the book, titled Spare, which will be available at bookstores in the UK next week, came as the book’s Spanish version was accidentally put on sale in Spain.

The Duke of Sussex, who has stepped down from his royal duties and left the UK with his wife Meghan Markle, flew during the war in Afghanistan and his missions resulted in “the taking of human lives.” He reportedly said in the book that he was neither proud nor ashamed of the killings as he described those killed as “baddies” who tried to kill “goodies.”

Prince Harry did not think of the 25 killed as “people” but as “chess pieces” that had been taken off the board, according to The Telegraph, which said it obtained a copy of Spare in Spanish.

Thousands of Taliban and Al-Qaida-associated militants were killed in the war in Afghanistan alongside thousands of civilians.

Prince Harry served in the British army for 10 years, rising to the rank of captain and undertaking two tours of Afghanistan.

In February 2008, Britain’s Ministry of Defense confirmed that Prince Harry had been serving with the army in Helmand, Afghanistan “for more than two months.”

"Prince Harry is very proud to serve his country on operations alongside his fellow soldiers and to do the job he has been trained for," a statement from Clarence House, a royal residence in London, said at the time.

The prince also reportedly claims in his autobiography that his brother, Prince William, and wife Princess Kate encouraged him to dress up as a Nazi soldier with a swastika armband, an incident that sent shockwaves across the UK in 2005.

Describing the event as “one of the biggest mistakes in my life,” Prince Harry says in the book that William and Kate “howled with laughter” when they saw him in the costume. By Ahmet Gürhan Kartal Anadolu Agency