Contact the internal affairs office of the police department in question and file a complaint. If the agency doesn't have such an office, talk to a member of department management. Finally, remember that just because you believe that a crime has occurred, doesn't automatically make it so. Let the professionals do their job. Well Nathan, there really isn't a simple answer to your question.
People steal for many different reasons.
Regardless of the exact reason, though, all thieves have one thing in common. That is, they have no respect for other people. People who steal are selfish and self-centered. Selfish people don't care if they hurt others by stealing from them. As you grow up, remember that everyone deserves to be treated with respect.