Call 911, for sure. Don’t yell “I just called the police!” But do yell “The police are coming! Here come the police!” Maybe point to the street as you do so. That might break up the mob without putting yourself at risk.
It also depends on who the bystanders are. Can they be shamed or otherwise talked into doing the right thing? Or are they moments away from being violent themselves?
It’s a tough situation any way you look at it...one decent person against a mob.
Better yet, yell “FIRE”. It gets a lot more attention.
That’s a good idea to yell “the cops are coming”. I’m going to remember that.