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: Tre's bicycle really needed new brakes. Sentence2: Tre saved up all his allowance to take his bike to the shop. Sentence3: On the way a teenager jumped Tre and stole all his money and his bike. Sentence4: Tre walked home crying and empty handed. Sentence5: When he got there he found his mother dead.
A teenager, His mother, Tre