King Charles III said the death of his mother Queen Elizabeth II on Thursday is a moment of "the greatest sadness" for him and his family.
"We mourn profoundly the passing of a cherished Sovereign and a much-loved Mother," Charles, 73, said in a statement. "I know her loss will be deeply felt throughout the country, the Realms and the Commonwealth, and by countless people around the world."
"During this period of mourning and change, my family and I will be comforted and sustained by our knowledge of the respect and deep affection in which The Queen was so widely held," he continued.
Buckingham Palace announced Elizabeth died Thursday afternoon at Balmoral Castle in Scotland at the age of 96. The palace announced hours earlier her doctors were “concerned for her health” and recommended for her to remain under medical supervision.
Members of the Royal Family, including Charles, William — now Duke of Cornwall and Cambridge — and Prince Harry traveled to Balmoral on Thursday to be by the queen’s side as her health declined.
Elizabeth was Britain's longest-reigning monarch and the first to reach 70 years on the throne after she became queen in 1952 at the age of 25.
Charles immediately became king upon his mother's death, and a Clarence House spokesperson told NBC News he will use the title King Charles III. His wife, Camilla, will likely take the title of queen consort after Elizabeth said it was her "sincere wish" for Camilla earlier this year.
"When, in the fullness of time, my son Charles becomes king, I know you will give him and his wife Camilla the same support that you have given me," Elizabeth said in a statement in February. "And it is my sincere wish that, when that time comes, Camilla will be known as queen consort as she continues her own loyal service."
Charles is expected to be officially named king by the Privy Council and Accession Council on Friday at St. James's Place in London, though his coronation could be months away — Elizabeth’s coronation after her father’s death didn’t happen until more than year after he died.