No one knows that until the game starts and they get their PMs.
Anyway, now that the game is over, I'll explain all that happened.
Before Caboose was hanged, I was discussing possible suspects with Connor (since obviously there's no way he could have been Mafia when the Mafia tried to kill him).
Among these suspects was Coldfreeze, due to his vehement defense of Caboose and poorly hidden desire to not see him lynched. This early in the game, who would have such a strong desire to protect another player from lynching? Only the Mafia know who is pro-town and who is anti-town.
And so Caboose was hanged. I then got the idea to put together a group of players to take down the Mafia. It would greatly increase our chances of winning, and it would work even if I died, which I was quite sure was going to happen. First, we needed to find out who the medic was.
This early in the game, no one had any leads, so the medic clearly either guessed at random, or was doing something quite common: Protecting her friends. I, naturally, had no idea. But he found out. The medic was Silent Alpha.
At first, in a funny twist, I forgot entirely about the concept of group PMs. On top of that, though I could easily send Alpha a PM at any time requesting protection, I didn't do so because I would feel bad if I requested medic protection for myself, and then was not the target.
Then, finding the detective. That was a very important part of this plan. I thought of people who couldn't be Mafia. And then it hit me. Caboose had voted for JXZAW before his panic, in other words, while he was still a faithful Mafian. So JXZAW couldn't possibly be Mafia.
So I took a guess. I asked him if he was the detective. He knew he could trust me because I wouldn't have voted to hang Caboose before his panic unless I were a civilian.
And he was.
I remembered group PMs and added him to the PM Connor and I were using, then the next day, I died.
Still, I had found the detective and got him together with a civilian everyone knew was innocent. And after my death, I added the medic too.
Thanks to Connor, JXZAW, and Silent Alpha. You truly have let all the Mafia hang.
We then proceeded to investigate and vote. I did a few things, like suggesting who to investigate, and suggesting that we not vote so as to cause a tie, so that we'd have a greater chance of finding a Mafian among the deaths. That worked quite well. I also advised against a vote that would have revealed JXZAW because Spartan was not on the suspect list. (He had investigated him without the slightest suggestion from me, a good move, but nearly voted to hang him at a bad time) Then after the tie hanging, my mind returned to Coldfreeze's suspicious activities. I asked JXZAW to investigate him.
With two Mafians dead, and two Mafians known, we had already won.