To feel guilty in such circumstances is entirely normal. I'm wondering what made you return there today? We cannot change the past though. Sometimes we reach out to help people but they reject our kindness and we have to put our cynicism behind us when the next opportunity to help someone arises. Perhaps this old man had lost his will to live, but we will never know. The fact that you are feeling so bad about it means that you aren't a bad person - what happened does NOT make you a murderer. It's a tragedy and let's hope that everyone can learn from reading about your experience.