Speaking from personal experience rather than with reference to any publication, I can attest that there is an extremely powerful stupefying effect that sets in when one is confronted with overwhelming force of arms, as was likely the case with the concentration camp victims you mentioned. Here is my short anecdote, for all it is worth.
A few years back I was among bank customers forced to assume the felony prone position in a bank lobby, as a delegation of heavily armed gentlemen in 3-piece suits emptied the full vault into a waiting van outside. As the operation wound down, the gang opened up with a variety of automatic weapons, firing into the ceiling both to keep their captive audience on best behavior, and to keep the cops at bay as the visitors prepared to depart with their cash withdrawal.
Suddenly forced to my feet as those booms rent the air while shell casings showered the floor, I was ordered into the air-tight vault, whereopun I remember suddenly feeling twice my age and completely uncoordinated as I shuffled my way towards the vault with the other captives, my mind dulled to a near catatonic state by the primal fear of suffocating to death in a sealed metal room. With the prospects of making a movie-style break for freedom foreclosed from the get-go, I will recollect that day as one in which I was essentially aboard for the ride, with absolutely no idea how it would all end, and not so much as the slightest inkling of how to change that fate for the better.
I hope this helps shed some light.