General Sani Abacha was found dead in his bedroom at the Aso Rock Presidential Villa in the early hours of 8 June 1998, aged 54. The official statement attributed death to a heart attack; persistent unofficial accounts (drawn principally from Major Hamza al-Mustapha's later confessions and from journalists including Joseph Lelyveld and Karl Maier) describe a poisoning at the hands of imported sex workers, with chief military aides allegedly complicit.
The Provisional Ruling Council convened the same morning and confirmed Chief of Defence Staff General Abdulsalami Abubakar as Head of State. Abubakar released most political prisoners, opened negotiations with the international community to lift sanctions, and announced an eleven-month transition culminating in the May 1999 handover to Olusegun Obasanjo.
Chief M.K.O. Abiola died in detention on 7 July 1998 during a meeting with a delegation of US officials led by Thomas Pickering. His death — also officially attributed to a heart attack — closed the June 12 chapter without an electoral resolution. Abacha's family was later compelled, in agreements with Switzerland (2005), Liechtenstein (2014), Jersey (2017) and the United States (2020), to return over $1.2 billion of looted funds.