Well, it looks like it was the right choice.
As I said, it looks you managed to prevent Mafia from performing the first NK, figured out the Mafia member who performed the kill, and by extension you've also basically managed to out their teammate by catching them so fast. It seems like in the OP we have two Power Roles for Town, and the other role is in an investigative role.
Given how many players Mafia would have to kill in order to win, it might be practically impossible for them to kill enough players before they're caught.
That's just how bad a situation things are for the mafia players right now with the N1 kill failing because of a role block.