Hi African_weasel,
I don't know you or what you could have done if anything, and I feel for you, and your friend. I do know that it will do no one any good if you beat yourself up, or are down on yourself for what you did or didn't do. It is not easy to not feel responsible when things around us or people around us end up in bad situations. People are ultimately responsible for themselves, and all we can do is help when we can, and focus on keeping ourselves together enough to be in a position to help others. Sometimes we are able to help and sometimes we are not. Just hang in there and do your best to focus on what you can do now, whether or not that is helping this person, or possibly helping someone else, or maybe even simply helping yourself. (By helping yourself you can put yourself in a better position to help others, its not selfish.) I know I have done more than just listen and apologize if I have given unwanted advise. Please take care, and be well.