Sigh some posts come up after my long one. Well I'll address a few things I saw.
Only in the last game. We don't know if he is or not in this game as well. Last game it was a measure given to serial killer to make them have a chance to win for once.A. Serial Killer is bullet proof, and doesn't side with mafia, he is an independent party.
Also the assassin bit, I'm not positive on it, but I thought they could do the night action of the mafia during the day by themselves. I believe the flash read (though someone double check to see) that they used the night kill of the next night for mafia as a day kill instead.
With a day vig in out midst though I'm willing to bet that the other night killing faction is a serial killer, as 2 mafia kills in a night is way over powered I think, unless town has some VERY nice power roles, which thus far are Day Vig, Inventor, masons, and govenor and maybe a Bulletproof townie.