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.

Sentence1: Justin was driving his black car down the road. Sentence2: He was speeding but he didn't realize it. Sentence3: The next thing you know he was pulled over by a cop. Sentence4: The cop told him he was going too fast. Sentence5: The cop wrote Justin a ticket and he was so ashamed.
Cop, Justin