After the condemned individual's personal information was checked and approved, he was handcuffed and led to a cell insulated with stacks of sandbags along the walls, and a heavy, felt-lined door. The victim was told to kneel in the middle of the cell, and was then approached from behind by the executioner and immediately shot in the back of the head or neck. The body was carried out through the opposite door and laid in one of the five or six waiting trucks, whereupon the next condemned was taken inside and subjected to the same treatment. In addition to muffling by the rough insulation in the execution cell, the pistol gunshots were masked by the operation of loud machines (perhaps fans) throughout the night. Some post-1991 revelations suggest prisoners were also executed in the same manner at the NKVD headquarters in Smolensk, though judging by the way the corpses were stacked, some captives may have been shot while standing on the edge of the mass graves. This procedure went on every night, except for the public May Day holiday.