But who? A political killing seems unlikely, not least because the former first lady was little more than a shadow to her husband's role as president. But there is politics and politics. A lot of South Africans have reason to be angry with the likes of Mrs de Klerk.
A lover? Marike de Klerk's choice of men was at times questionable. After her divorce she took up with a Johannesburg businessman, Johan Koekemoer. They lasted eight months until coverage of their engagement prompted several of his former acquaintances to allege that he was a con man and wanted for fraud. A week later Mr Koekemoer took off.
Mrs de Klerk never criticised her husband openly and said she would still stand by him even after he publicly confessed to an affair with the wife of a shipping tycoon and said he wanted to end their 38 year marriage.
"I told him: 'If you change your mind, I'll forgive everything - up to 70 times seven," Mrs de Klerk wrote in her autobiography. "He whispered: 'I'm certain about my decision. Stop hoping'."
Deeply religious
A deeply religious woman from an orthodox Afrikaner family, she was racist and privately had a difficult time accepting the reforms instituted by her husband after he released Nelson Mandela from prison in 1990. She once described mixed-race or "coloured" people as "left-overs".
"You know, they are a negative group … a non-person. They are the people that were left after the nations were sorted out. They are the rest," she said.
In 1990, one of the three de Klerk children, Willem, announced his intention to marry a "coloured" woman, Erica Adams. His mother pressed him to end the engagement by, among other things, telling him that it could jeopardise FW de Klerk's political reforms by undermining white people's confidence in him.
Mrs de Klerk once said that Margaret Thatcher was her hero. That view was not shaken by a visit to Downing Street at which the prime minister ignored Mrs de Klerk until the discussions with the South African president turned serious. At that point the prime minister turned to Mrs de Klerk and said: "Marike, I think you should go shopping now."
The loss of power and status did not come easy with the transition to democratic rule in 1994. Mrs de Klerk quickly grew to dislike Nelson Mandela over what she saw as attempts to humiliate her over where South Africa's last white president should live.
In his autobiography, FW de Klerk said it was a matter of "supreme indifference" to him. "But not Marike. She was deeply distressed by all the chopping and changing which she interpreted as a calculated attempt by Mandela himself to humiliate us," he wrote.
Mrs de Klerk went on to found the Women's Outreach Foundation, a controversial organisation which accused ANC leaders of lavish parties and being unfit to govern. The ANC responded by calling the ex-president's wife "a bitter person unable to come to terms with the fact that she is an ex-first lady of this country."
But Maretha Maartens, who ghost wrote Marika de Klerk's autobiography, said it was the former first lady's personal life that made her most unhappy. Speaking yesterday after news of the murder broke, she said that Mrs de Klerk had often contemplated death.
"She missed FW a lot and she was extremely lonely. She said to me once or twice that life was not worth living and that it would be better if she were dead," she said.