Depends probably on your location. In a lot of countries (for example Germany) you are obligated to give first aid (independent of yourknowledge) . You can even be sued for not helping in an emergency.

This is the case for licensed medical practitioners in the US as well, including doctors and nurses. If a Flock camera catches the sister leaving the scene of an accident, and the sister is an RN, the sister can be civilly liable and possibly even criminally culpable for refusing to render aid within her professional scope.