from 1 bullet to 3???

[pop2-4]

Am I missing something?  When the man was remembering his last conversation with his wife he stated he had two bullets in the gun.  He then used one when he shot the bandit in the head, leaving only one.  Later in the book after talking about the dog following them for two days it was stated "there were three cartridges left in the pistol. None to spare."  Where did the two extra cartridges come from?