I must have missed the 'at speed' part in the report.
It doesn't take much to kill a frail or elderly person - 10mph impact by a moto could easily do it.
Sounds like the rider might not have been found at fault had they stayed. One can only imagine what factors caused them to run (speed, DUI, unlicensed, stolen, unregistered, or uninsured bike, outstanding warrant, etc).
But for those who don't live in SF, you might not understand just how rampant double parking has become. You can not go half a mile without having to go around someone. Some are more cautious than others, but it is never entirely safe.