Bagosora wahoze ari Coloneli mu ngabo za FAR, wari ari kurangiriza igihano cy’igifungo cy’imyaka 35 muri Mali kuva ku ya 1 Nyakanga 2012 yapfuye.
Amakuru y’urupfu rwa Bagosora yemejwe n’umuhungu we Achille Bagosora abicishije ku mbugankoranyambaga akoresha
Yatawe muri yombi ku ya 9 Werurwe 1996 muri Cameroun, ajyanwa i Arusha tariki 23 Mutarama 1997.
Tariki ya 18 Ukuboza 2008, Urugereko rwa Mbere rw’Iremezo rw’urukiko mpuzamahanga mpanabyaha (ICTR), rwahamije Bagosora ibyaha bya Jenoside, ubwicanyi, gutsemba no gutoteza nk’ibyaha byibasiye inyokomuntu, gufata ku ngufu n’ibindi byaha, rumukatira igifungo cya burundu.
Ku ya 14 Ukuboza 2011, Urugereko rw’Ubujurire, icyo gihe rwari ruyobowe n’umucamanza Theodore Meron, rwagabanyije igihano cy’igifungo cya burundu, rumuhanisha gufungwa imyaka 35.
Muri Werurwe 2019, Théoneste Bagosora yatanze icyifuzo cyo kurekurwa mbere y’uko asoza igihano cye, ikifuzo cye cyatashejwe agaciro.
Col. Theoneste Bagosora afatwa nk’umwe mu ncurabwenge za Jenoside yakorewe Abatutsi hashngiwe ku bikorwa n‘amagambo yamuranze mbere gato y’iyi Jenoside.
Ku wa 9 Mutarama 1993 i Arusha muri Tanzania ubwo hari hamaze gusinywa igice cy’amasezerano ya Arusha kirebana no kugabana ubutegetsi, Bagosora yasohotse arakaye aravuga ati “Ndatashye ngiye gutegura imperuka (yakoresheje ijambo ry’igifaransa Apocalypse)”. Bivugwa ko kandi ubwo yari mu mishyikirano ya gisirikare yabereye i Byumba ahitwa i Ngondore, yeruye ko nta mututsi uzakandagira mu Ngabo z’u Rwanda icyo gihe.
Bagosora yavukiye i Giciye ahahoze ari Akarere ka Nyabihu , Intara y’Iburengerazuba , u Ruanda. Mu 1964 yarangije muri École des oficiales (Ishuri rya Ofisiye) i Kigali afite ipeti rya liyetona wa kabiri, akomeza amasomo ye mu Bufaransa. Mu mirimo ye ya gisirikare yabaye umuyobozi wa kabiri wa militaire ya École supérieure (Ishuri Rikuru rya Gisirikare) i Kigali ndetse anayobora ikigo cya gisirikare cya Kanombe.
Yashyizwe ku mwanya wa minisitiri w’ingabo muri Directeur du cabinet (umuyobozi mukuru) muri Minisiteri y’Ingabo muri Kamena 1992. Nubwo yavuye ku gisirikare ku mugaragaro ku ya 23 Nzeri 1993, yagumanye uyu mwanya kugegau muri muri 1994.
