 Ahavuye isanamu, AFPGetty Insiguro yisanamu, Si ubwa mbere Bwana Shekau ashikiriza ubutumwa abicishike muri video Shekau - asanzwe arongoye Boko Haram haciye imyaka icumi - yaragiriraniye amasezerano numurwi IS mu mwaka wa 2015. 