In a 3 player Assassin game it's obvious who is set out to kill you and vice versa...
My suggestion would be to disable 3 player games for this amount of players.
C.
PS Here's the logic...
Player A is Targetting Player B.
Thus Player B must be targetting Player C
and Player C must be targetting Player A
Why?
If Player B was targetting Player A then Player C would be targetting themselves.