Zindzi Mandela, the daughter of former South African president Nelson Mandela and activist Winnie Mandela, has passed away. South Africa’s ambassador to Denmark was 59 years old.

According to the Associated Press, local television outlets reported that Mandela died at a Johannesburg hospital early Monday morning. The cause of death is expected to be released in detail at a later time. 

In a statement from the Nelson Mandela Foundation, the organization remembered the celebrated activist as a great friend to the organization and a “special soul” who lived a rich and extraordinary life. “She worked with the Foundation on many projects over the years,” the organization added. “We valued her generosity, her warmth and her sense of humor. 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.”

Mandela rose to international prominence during her father’s incarceration at Robben Island. In 1985, the former president, then a prisoner, rejected the government’s offer to release him upon the condition that he denounce violence by his associated political party, the Africa National Congress. It was Zindzi who read the letter he wrote for a public broadcast.

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“With South Africa in the depths of a brutally enforced State of Emergency, Zindzi’s speech in Soweto, on behalf of her father, rejecting PW Botha’s offer of a conditional release, reinvigorated the values and principles of the struggle,” read a statement from the Desmond & Leah Tutu Legacy Foundation. It added that with her death, the country of South Africa “loses an important generational link connecting our divided history to the promise of better, more inclusive, tomorrow.” 

Zindzi Mandela’s death comes just days before the country was set to celebrate her father’s July 18 birthday. According to the Nelson Mandela Foundation, her passing also comes on the exact day of her brother’s fatal car crash in 1969. 

Dignitaries, celebrities and activists have flooded social media with remembrances for Mandela, highlighting her pivotal work in the fight for Black South Africa’s liberation.