Mafia 54. This is where caravans are robbed!

I think I know who wrote the note yesterday, pretending to be player 4. Instead of writing a note about staying home, it would have been logical to write that Sab is not a Mafia member. Besides, player 4 doesn't even participate in the game; he just gives orders. It also seems strange for a Mafia member to write such a note... what's the point of it?
I don't know who to execute.