UPDATE: On May 24 Shanghaiist corrected its earlier story. Things were not as bad as described in the original email that they received. Although one person unsuccessfully tried to attack the volunteer and the crowd indeed surrounded his taxi (quite scary experience, I think), he was not physically harmed in the incident. I sincerely hope that this was an isolated incident and that things will calm down soon in China.
In order to avoid other media from using this story I have decided to delete the original blog post. You can still read the original article on Shanghaiist here.