Albertina Sisulu, a major player in the struggle against apartheid, has died at her home in Johannesburg, South Africa, family members said. She was 92. A son, Mlungisi, said she was sitting in a chair watching the news while dinner was being prepared Thursday when she slumped over and died, the British newspaper The Independent reported. \"I think I\'m still in shock, because I was talking to my sister who was in the same room with her and she said she was fine, and the next 20 minutes you hear that she passed away,\" said Beryl, another of her children. African National Congress spokesman Brian Sokutu said the party is \"shocked and saddened by the passing away of one of our longest-serving stalwarts of the liberation movement.\" \"Comrade Sisulu dedicated all her life to the ANC and the people of South Africa so that today we can celebrate having defeated the tyranny of apartheid and having ushered in constitutional democracy,\" Sokutu added. Sisulu was the widow of Walter Sisulu, who was a friend and mentor of former South African President Nelson Mandela. The BBC said she was known as \"Ma Sisulu\" in South Africa. \"While we mourn her loss, we must thank her most profoundly for the selfless service to all South Africans and humanity at large, for her generosity of spirit and for teaching the nation humility, respect for human dignity and compassion for the weak, the poor and the downtrodden,\" South African President Jacob Zuma said.