Mayombo, who was serving as Permanent Secretary in the Ministry of Defence at the time, had built a reputation as an intelligent and influential officer within the Uganda People's Defence Force.
He rose through the ranks after joining the bush war led by Yoweri Museveni in 1985, later serving as Chief of Military Intelligence and as a key figure in both security operations and political processes, including the Constituent Assembly that shaped Uganda’s 1995 Constitution.
His sudden illness began in Kampala, where he reported severe abdominal pain before being admitted to International Hospital Kampala.
He was later flown to Nairobi for specialised treatment but died shortly after arrival at Aga Khan Hospital. The official cause was acute pancreatitis, which led to multiple organ failure.
However, his death quickly became the subject of national controversy.
Public speculation intensified after President Museveni suggested during funeral proceedings that Mayombo may have been “targeted by a criminal clique”, prompting an official investigation.
Although the government later stated there was no evidence of poisoning, the findings were never fully made public, leaving lingering questions that persist years later.
Nearly two decades on, Mayombo is still remembered as a disciplined officer, skilled lawyer and influential insider whose rapid rise had positioned him among a generation of leaders seen as shaping Uganda’s future.