After re-reading everything to compile my thoughts
Of the two bullet deaths yesterday, I believe the guards killed one, and GK killed the other, hence the empty gun.
GK's death with the knife has to be the town vigilante. And from all the descriptions, he's still in the game.
If we are to believe @Qupax, there's a roleblocker in the game. I'm still suspicious of him from Day 1, but I don't see a reason not to believe this claim as that is a common ability
@Jumbo's aggression early into Day 1 makes me very suspicious of him. I think @brightfalls and Dacder going at it yesterday in their 10 page semi-erotic "will they or won't they kiss" back and forth were just two prisoners doing exactly what the guards wanted them to do and Guard Jumbo jumped on a potential obvious lynch target to try and get a train rolling.
Gun - I trust @Hagan with the weapon if he's willing to accept.