I do not think what you said is incorrect. One would think your reaction to seeing others killed like that would be more radical than calmly accepting your fate. Too many methods of making someone as numb as these prisoners to speculate a specific method used. The more likely scenario (imo) is mock executions are more common with single prisoner execution. Sometimes knowing your fate, is major freedom from the horrible parts of ones mind as well. Knowing you are about to die can put you in a euphoric state if you do not fight it. I only know this from multiple books from authors who's lives have been spent curious and looking for answers on death. If you ever get a chance and are not familiar with alan watts, you should check out his books. Great reads and some describe acceptance and death in great detail.