The emperor 's first minister was his powerful uncle , Soga no Umako .
It is said that one day , he saw a wild boar and proclaimed , `` I want to kill Soga Umako like this wild boar . '' This angered Soga no Umako and , perhaps out of fear of being struck first , Umako had Sushun assassinated by Yamato no Aya no Ataikoma in 592 .