ˈd(y)o͞odē noun 1. a moral or legal obligation; a responsibility. synonyms: responsibility, obligation, commitment
2. a task or action that someone is required to perform. synonyms: job, task, assignment, mission, function, charge, place, role, responsibility, obligation
As a Range Officer you have a duty to keep those coming to your range for recreation or training safe from themselves, keep the event under control, make sure range rules are being followed, and ultimately ensure that no one is endangering the safety of others. The idea that "everyone is a range officer" is incorrect. The fact that everyone is responsible for their own actions, however is true. The duties of a Range Officer are different than the responsibilities of those attending the training event.