What I did:
-Kill captain and everyone in that corridor (I did it at the beginning of the mission just to use the captain room to use it as a body dumpster, I didn't knew the prisoner would get escorted there).
-Get both papers, get prisoner escorted.
-When they enter the corridor where the captain room is, shut all doors, shoot both troopers in the head.
-Take bodies and prisoner to dumpster.
-Tell him to wait there.
Now biggest problem is the SS captain that keeps popping in an out of a room full of officers to smoke his cigarettes.
-Close door just by that room. Attract sentry by running near the closed room when SS captain is INSIDE. Sentry will come investigate. Close door as he enters, choke him to death. Hide body.
-Repeat same trick when SS captain is OUTSIDE. He'll get attracted as well. As he opens the door shoot him (as he's not directly in front of the room full of officers they won't see him fall).
-Close door of officers room.
-Go to the exit, kill both guards.
-Come back, take prisoner, walk away.
Prisoner freed, no alarm raised
