Given the task definition and input, reply with output. 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: Bobby was downloading music to his computer. Sentence2: He was downloading it from a shady site. Sentence3: Bobby began to have trouble with his computer. Sentence4: He had downloaded a virus. Sentence5: Bobby had to bring his computer to an expert.
An expert, Bobby