SCOTUS has spoken five (5) different times, asserting that the police have no duty to protect any specific person, and in at least one case that the police have no duty to actually respond to a 9-1-1 call.
That the vast majority of people do not know about this is tragic in both senses of how that word is used here.
You are on your own until the police arrive to document the scene and interview any potential witnesses. If they happen to arrive while to problem is still occurring, and if they decide to intervene, you may count yourself as exceedingly fortunate.
stay safe.