He then studied at Saint Vincent Minor Seminary Rulindo from 1977 until 1983 for his secondary school education.
He graduated with a Doctorate in Dogmatic Theology from the Faculty of St. Thomas, in Capodimonte (Naples), Italy.
[1][2] As a priest, he held various positions inside and outside his diocese including as:[2] During the Rwanda Genocide of 1994, Father Célestin Hakizimana was the Parish Priest at Saint Paul Catholic Church in downtown Kigali City.
He is credited with saving the lives of over 2,000 Tutsi refugees who had run to Saint Paul Church for sanctuary.
That administatorship ceased when Bishop Edouard Sinayobye was installed at Cyangugu as the Ordinary, on 25 March 2021.