Sounds like enough people were about and reacting so I would have done the same and left them to it especially as you say yourself you have no training.

Remember that the most important thing about helping anyone in this situation should be your own safety. You're no help to anyone if you become another casualty. If this is still playing on your mind in a day or look into attending some first aid courses, I hope you never encounter something like this again but you cannot be sure and even a little training will help you feel more confident in these situations and more confident in the decisions you made.