Originally Posted by Vengeance
Of course he knew. Kisame said so himself I know everything about you or some shit. He was assigned to Itachi to watch over him & kill him if necessary more likely than not.
we all saw the flashback they boh each others past but when kisame threaten him itachi brought out his ms and threaten kisame right back. so i think they were both given the same mission if either one of them got soft the other was meant to kill the person who got soft in my opinion.