As soon as I've interogated Sam and leave the torture chamber the Sheriff starts to attack me for no reason. It seems like a bug but I'm not sure. What am I suppose to do now? If the Sheriff dies I wouldn't be able to interogate more people, probably breaking the game.

Im having the same problem i didnt think it was a bug so i killed him and now my whole game is screwed. is this a bug or where do i go from here as i cannot interrogate the judge now

It does sound like a bug to me. It would probably be best to contact the developpers about it.

Apparently it only happened if you let a paladin or soldier get attacked by Sam so I lured I ran a little to the right and he followed then I killed him before any guards could intervene and then it worked, the Sheriff stopped the attacking.

As for you Fortyouncee, you'll probably have to reload or restart as killing a main quest character would probably break the game.