(CNN) -- A former mayor in Rwanda has been convicted of genocide and extermination as a crime against humanity over the deaths of 2,000 Tutsis during the country's 1994 genocide, the U.N.-backed International Criminal Tribunal for Rwanda said Thursday.
Former Kivumu mayor Gregoire Ndahimana served as a leading facilitator and commander in the slaughter of Tutsis in Kivumu, where an estimated 4,000 Tutsis were murdered, according to the ICTR's Summary of Judgment.
According to the judgment, Ndahimana was present during a massacre at the Nyange Catholic church where 2,000 Tutsis died over 10 days from 6 April 1994 to 16 April 1994, in one of the bloodiest sites of the genocide.
His presence "had an encouraging effect on the principal perpetrators," particularly because he was an authority figure, the tribunal found, ruling that he "aided and abetted genocide."
Ndahimana was also found guilty of "extermination as a crime against humanity by aiding and abetting as well as by virtue of his command responsibility over communal police in Kivumu," the judgment said.
Ndahimana was sentenced by a majority of the Trial Chamber's three-judge panel to a single sentence of 15 years imprisonment, the ICTR said, with credit for two years already served.
"The Chamber has considered the gravity of each of the crimes for which Ndahimana has been convicted," the judgment said.
Gruesome reports by survivors and other witnesses accused Ndahimana of joining local police and a priest in ordering assailants to bulldoze Nyange church, killing 2,000 Tutsi refugees who had sought sanctuary there.
A majority of the judges ruled that Ndahimana was present during the demolition of the church, but did not find it proven that he instigated or supervised the attacks.
A trained agronomist, Ndahimana served as "bourgmestre" of Kivumu, a commune in the prefecture of Kibuye near Lake Kivu.
According to a United Nations study, at least 59,050 people, or 12.4% of the Kibuye population, were killed during the genocide, accounting for more than three-quarters of the prefecture's Tutsi population.
The Rwandan genocide was triggered by the April 6, 1994, shooting down of a plane carrying the nation's Hutu president.
Ethnic violence erupted and Tutsis were killed systematically by Hutus over the course of three months.
The United Nations estimates that some 200,000 people participated in the perpetration of the Rwandan genocide.
In all, some 800,000 men, women, and children -- mostly Tutsis but also moderate Hutus -- died.