Your position in life won't be a barrier for you to help people. As a janitor, you must know your place first, it will not work if you just stop the bully. The bully won't listen to you. It is better to report it to the higher authority, and they will deal with the problem. You still helped in the sense that you didn't keep your mouth shut about what you saw, but instead, you did all you can to help which is to tell it to the powerful ones.