"Bystanders Who Aided A Woman In Trouble Are Injured"
This incident occured in Melbourne on the corner of of Williams St and Flinders Lane outside of a cafe. This occured in the middle of Melbourne and during peak hour traffic on a monday morning.
I agree that calling the police would be a sensible option, however there may be implications if the person in trouble would soon disappear out of your sight. For example, if the lady and man both got into a taxi.