her pistol scoots away and stops short of the porch and skid backs away from her and is still backing away when an officer in a blue cap with brown furred ear-flaps folded up and strapped across the top , and wearing quilted , blue coveralls with fbi stenciled on the back , passes him on the right , his bare finger curling from a blue knit glove around the trigger of an automatic rifle , his eye aiming down the barrel and his shoulders squaring at every window of the mess hall one at a time and at the door .