In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.
Q: Sentence1: Jack was on a patrol outside base camp in Afghanistan. Sentence2: Suddenly a bullet zipped by his head, lodging in the wall behind him. Sentence3: Jack snapped down his night vision goggles, looking for the shooter. Sentence4: Jack found him crouching near the ground. Sentence5: Jack fired his rifle, killing the man who shot at him.
A:
Shooter, Jack