Britain and the world are in mourning after the longest-reigning monarch in the country's history, Queen Elizabeth II, passed away Thursday.

Her death was confirmed in a statement by the royal family saying she died "peacefully," and the crown had passed to her eldest son, now King Charles III.

In the wake of her death, tributes from around the world, as well as anecdotes from her 70-year reign, are being widely shared.

One poignant moment that has resurfaced is the tribute she herself paid to the victims of the September 11, 2001, terror attacks in the United States.

The monarch broke with centuries-old tradition, directing the Coldstream Guards to play the American national anthem, "The Star-Spangled Banner," during the Changing of the Guard at Buckingham Palace.