This exact thing happened to me on my way to work around 4 years ago — a young woman was hit on her bike at the intersection of Mission and Fremont (https://goo.gl/8DW76r). Myself and 2 other strangers tried to help, to perform CPR. A crowd gathered around. People yelling advice or criticisms at us from the sidelines. No helmet — not sure it would have helped — so there was blood and other fluids on the street, and on us. We tried, in vain — CPR was never going to be enough. I sat on the corner for a good while after she was taken away, and later, finally, broke down. It still upsets me when I think about it deeply. Being there, touching a body, as a soul moved on from this world. I’d never experienced anything like that before.