Question

what happened to the gunner and old woman in the chapter sniper

Answer 1

The old woman in question is actually an informer working for the Free Staters.  While the Republican sniper is under fire from the opposing Free Stater sniper, he sees an armored car pull up near his position.  The Republican sniper sees an old woman in a shawl approach the vehicle.  She begins talking to the soldier in the vehicle, and then she points toward his own position.  
Then round the corner of a side street came an old woman, her head covered by a tattered shawl. She began to talk to the man in the turret of the car. She was pointing to the roof where the sniper lay. An informer.

This puts the sniper in a very tough position.  He is now pinned down by another sniper, and ground forces have been alerted to his position.  In order to get out of his predicament, the Republican sniper needs to kill everybody that knows his position.  That means he must kill the man in the armored vehicle, the old woman, and the other sniper.  The Republican sniper does exactly that, and he does so in that order as well.  

The turret opened. A man’s head and shoulders appeared, looking toward the sniper. The sniper raised his rifle and fired. The head fell heavily on the turret wall. The woman darted toward the side street. The sniper fired again. The woman whirled round and fell with a shriek into the gutter.