Forget all the PR and legal mumbo jumbo....let's take this operationally for a moment.
1. Did you have a plan for IF someone DID need help or had serious injuries?
2. Did you notify YOUR company/organization where you were, what you saw and that you were stopping?
3. If above, did you ASK them for permission or advice on whether you should stop?
4. Does your company have a policy on this type of situation you could have defaulted to? If so, why didn't you?
5. Why were you out of area in an ambulance solo? If this is a regular occurrence then above mentioned policies need drafting.
6. Assuming you did not notify anyone above, what was your plan if you got out and someone was in crisis? Now you would leave them to go an dnotify the proper authorities? Did you also call 911 so you could give updates to whoever was responding?
7. Do you know who was responding? Do you know what county or service provider's area you were in?
These are just a few of the MANY more questions I have, I literally could go on for pages and this is all OPERATIONAL planning and procedural stuff. Again, omitting discussion of legal liability, scope and PR.
Do you think or understand how woefully under prepared you were for this situation? In hindsight after reading these questions and the other comments, is there anything you have learned or would have done completely different?
If I were to get to the legal liability part, let's say one of those "noninjured" folks becomes an opportunist. What documentation do you have to support what you saw, what you did, what you asked? Sure, you rolled up on it and stopped as a "good sam", however you are there representing your organization as well. They will bear some liability in any claim made especially if a shrewd lawyer is able to convince them you were unprepared, uneducated, untrained to the extent where you did not do what you were supposed to do. There are so many things that could go sideways from this event.
At a minimum, I would call 911 so you get the county or service area you are in, state who you are, who you represent and you are stopped at a MVC located at XYZ Junction. Inform them you will ask a few questions of the involved parties and you will call back and update them or remain on line while you do it. It is all recorded.
Just a lot of food for thought amigo.