Zindzi Mandela — the youngest daughter of anti-apartheid icons Nelson and Winnie Mandela — has died at the age of 59. According to a statement from the South African Department of International Relations and Cooperation, Zindzi, who served as South Africa’s Ambassador to Denmark, passed away Monday morning at a hospital in Johannesburg (July 13).

“Zindzi will not only be remembered as a daughter of our struggle heroes, Tata Nelson and Mama Winnie Mandela, but as a struggle heroine in her own right. She served South Africa well,” the Minister of International Relations Naledi Pandor said.

The cause of Zindzi’s death is not yet known, as the department is expected to release a more detailed statement later on.

President of South African Cyril Ramaphosa also offered his condolences to the Mandela family in a statement on Monday (July 13).

“We mourn the passing of a fearless political activist who was a leader in her own right,” he said. “Our sadness is compounded by this loss being visited upon us just days before the world marks the birthday of the great Nelson Mandela.”

The Nelson Mandela Foundation issued its own statement on Zindzi’s passing, saying that it would remember her as “a special soul.”

“Zindzi will be remembered for a rich and extraordinary life, marked by many iconic moments,” the statement read. “… We valued her generosity, her warmth and her sense of humour. She was always patient in responding to our requests for information and other forms of assistance. And we admired her strength in dealing with life’s challenges and tragedies.”

Tragically, Nelson Mandela’s oldest son Madiba Thembekile Mandela also passed away in a car accident on this day in 1969. Saturday (July 18) will mark what would have been Nelson’s 102nd birthday. The former South African president died at the age of 95 in 2013.