He was chiefly known for his key role in the 1994 Rwandan genocide for which he was sentenced to life imprisonment by the International Criminal Tribunal for Rwanda (ICTR).

It seems that, in as much as there was a general organizer of the whole operation, this distinction has to go to Colonel Théoneste Bagosora.Bagosora was born in the same northern region as Juvénal Habyarimana, the president of Rwanda from 1973 to 1994.

He was linked to le Clan de Madame, known later as the akazu, a group associated with Agathe Habyarimana, the president's wife, who was at the nexus of the Hutu Power ideology.

[9] Luc Marchal, a Belgian officer, who served as Kigali sector commander in UNAMIR, reported that Bagosora told him that the only way to solve Rwanda's problems was to get rid of the Tutsi.

[11] At about 8:15 pm on the evening of 6 April 1994, President Habyarimana was flying back to Kigali after a meeting when his plane was struck by two missiles fired from the ground.

The position of the American and Rwandan governments is that the missiles were fired from the Kanombe barracks, which were controlled by the Presidential Guard, but that conclusion is disputed.

[14] Dallaire rejected Bagosora's proposal of having the military take control of the political situation until they could hand it over to the politicians and he reminded him that Rwanda still had a government headed by Prime Minister Agathe Uwilingiyimana.

On the morning of 7 April, ten Belgian peacekeepers who had been guarding Prime Minister Agathe and who were witnesses to the government troops laying siege to her residence were disarmed and taken to Camp Kigali, approximately 200 metres from where Colonel Bagosora was holding a meeting of military officers.

"Fed and protected in refugee camps supported by millions of dollars in international aid, the Hutu Power leaders were able to hold regular planning meetings and to recruit new members.

During his trial further evidence was submitted that in 1991 he and other co-accused helped to draft a document where they referred to the Tutsi ethnic group as the "principal enemy" which was widely distributed in the army.

[19][20] In ruling that life imprisonment was the appropriate sentence for Bagosora the three trial judges concurred that "The toll of human suffering was immense as a result of crimes which could have only occurred with his orders and authorisation.

[22] The court ruled that Bagosora was responsible for the murders of Prime Minister Agathe Uwilingiyimana, the ten Belgian peacekeepers who had been guarding the Prime Minister at Camp Kigali, the president of the Constitutional Court Joseph Kavaruganda, and three major opposition leaders, Faustin Rucogoza, Frederic Nzamurambaho, and Landoald Ndasingwa.

In the 2007 film Shake Hands with the Devil, a dramatisation of Canadian military officer Roméo Dallaire's book about his time as commander of the United Nations Assistance Mission for Rwanda, Bagosora is portrayed by Burundian actor Michel-Ange Nzojibwami.