You could check in the PlayerTouched function to make sure the player returned from Players:GetPlayerFromCharacter() is not the tool owner by doing something like
local Player = game:GetService('Players'):GetPlayerFromCharacter(Parent)
if Player and Player ~= TOOLOWNER then
return
end
Depending on if the kill part is a descendant of the tool, you could grab the toolowner by doing Players:GetPlayerFromCharacter(script:FindFirstAncestorOfClass('Tool').Parent) to grab the player who currently has the tool equipped