two hundred and fifty pounds of moving mass , a huge fist , a huge impact , the zipper of the guy 's coat driving backward into his breastbone , his breastbone driving backward into his chest cavity , the natural elasticity of his ribcage letting it yield whole inches , the resulting violent compression driving the air from his lungs , the hydrostatic shock driving blood back into his heart , his head snapping forward like a crash test dummy , his shoulders driving backward , his weight coming up off the ground , his head whipping backward again and hitting a plate glass window behind him with a dull boom like a kettle drum , his arms and legs and torso all going down like a rag doll , his body falling , sprawling , the hard polycarbonate click and clatter of something black skittering away on the ground , reacher tracking it all the way in the corner of his eye , not a wallet , not a phone , not a knife , but a glock 17 semi-automatic pistol , all dark and boxy and wicked .