On 16 April 1994, at the start of the genocide against the Tutsi, he was appointed chief of staff of the army and promoted to the rank of major general.

Bizimungu was born in Byumba préfecture, Mukarange Commune, Mugina Secteur, Nyange Cellule, Rwanda.

Some days later, in the wake of Déogratias Nsabimana's death alongside Juvénal Habyarimana, Bizimungu was promoted to major general and appointed as chief of staff of the Rwandan Army of the FAR, replacing Marcel Gatsinzi.

"[5] On 12 April 2002, the International Criminal Tribunal for Rwanda (ICTR) issued an arrest warrant for Bizimungu, who was apparently working with the Angolan rebel movement UNITA.

[6] The trial adjourned until September 2008, whereupon Bizimungu was tried along with fellow FAR officers Augustin Ndindiliyimana (Chief of Staff of the National Gendarmerie), François-Xavier Nzuwonemeye (Commander of the Reconnaissance Battalion of the Rwandan Army) and Innocent Sagahutu (Second-in-Command of the Reconnaissance Battalion of the Rwandan Army).