 Why doesn't Zarwell shoot Bergstrom?
It took him only a few seconds to push the case into the compartment, lock it and slide the key along the floor beneath the locker. The floor continued its transmutation, and Zarwell sank deep into viscous depths. Now Zarwell was fleeing, pursued by the same bearded men who had been his comrades before. A WORK truck picked Zarwell up the next morning and he rode with a tech crew to the edge of the reclam area. When Zarwell arrived, six months before, the vitalized area already extended three hundred miles along the coast, and sixty miles inland. After its three-thousand-mile journey across scorched sterile rock, it sucked the moisture from a man’s body, bringing a membrane-shrinking dryness to the nostrils as it was breathed in.
 Zarwell is a freedom fighter, not a cold-blooded killer.
 Zarwell may have been a killer in the old life, but not now.  Zarwell is trying to start a new life. He doesn't want to kill anymore.  Zarwell is a freedom fighter, not a cold-blooded killer.  Zarwell likes Bergstrom. They are friends.