The unnamed previous owner of the Samehada (likely a member of the Seven Ninja Swordsmen of the Mist) was a high-ranking shinobi of Kirigakure, who had Kisame Hoshigaki as his subordinate. He, like Kisame, had shark-like attributes, but is of a more rotund body. Assigning Kisame to the secret intelligence squad, he ordered him to protect his comrades but, more importantly, codes that are important to their village. With this set of priorities, Kisame resolved to massacre his own teammates when they were in danger of falling into the hands of Ibiki Morino during a mission to protect such information.
Later, this superior was revealed to be leaking information to the enemy, and was killed by Kisame when he let his guard down during a meeting (his corpse visibly impaled by sharp implements tied to chains). Kisame would then take Samehada for himself, becoming a member of the Seven Swordsmen (aside from working as Yagura's and Madara Uchiha's personal hatchet-man.)
This article is a stub. You can help the Narutopedia by expanding it, or perhaps you could contribute to the discussion on the topic.