During the long speech with Karen outside the snow keeps stopping between shots.
Tom, Dai, and Pope are searching the basement when they hear a noise coming from a vent. In a common Hollywood trope, Pope racks the slide on the shotgun he is carrying to chamber a shell. This would mean that he was walking in a hazardous environment with basically an empty gun, something that any fighter let alone a 'Berserker' would never do. When they get Matt out of the vent and Pope moves to engage the Crawlies he racks the slide again, which would have ejected the live shell he previously loaded. Again, something that any fighter would not do as this would be a waste of ammunition. Hollywood likes to use the distinctive sounds of a shotgun racking a shell, as well as the 'hammer' being drawn back on a pistol even when the pistol has no hammer.