King Charles and Queen Camilla were left "shocked and saddened" this week following the tragic school shooting which took place in Graz, Austria, on Tuesday.
The suspected gunman, a 21-year-old Austrian man, shot dead eight pupils and an adult at his old high school and injured several others before taking his own life. Local media later reported that a tenth victim subsequently died after being left in a critical condition.
In a joint statement, which was shared to Instagram on Thursday, the royal couple wrote: "My wife and I were deeply shocked and saddened to learn about the appallingly tragic events at the Dreierschutzengasse school in Graz.
"Schools should be places of sanctuary and learning, which makes this horrific attack on students and staff all the more dreadful."
It continued: "Our most heartfelt thoughts and prayers are with the families of all those affected by this terrible loss of life and injury. We send our deepest sympathy to all Austrians at this profoundly distressing time."
Following the ordeal, Austrian Chancellor Christian Stocker said there would be three days of national mourning, with the Austrian flag lowered to half-mast on all buildings and a national minute of mourning taking place at 10am on Wednesday.
On Tuesday, locals lit candles and placed them in the main square of Graz city centre in a heartfelt tribute.
President Alexander Van der Bellen said in a statement: "This horror cannot be captured in words.
"These were young people who had their whole lives ahead of them. A teacher who accompanied them on their way."
King Charles' Trooping appearance
The monarch will make an appearance on Saturday at his annual birthday parade. In a break with royal tradition for a second year in a row, Charles is set to ride in the carriage procession instead of on horseback.
According to The Times, the monarch may have hung up his riding boots for good.
He rode horseback as sovereign for the first time in 2023 – also marking the first time a monarch had ridden in the parade since Queen Elizabeth II in 1986.