You are on your own.
SCOTUS has ruled many times the police have no duty to protect any one individual. Society as a whole, yes, individuals, no.
And thus if you call 911 and no one comes, to bad. Does not matter how many times you call, how bad you are off. You are SOL if they can't come. And in many many places, there are so few cops, well, it will be anywhere from 10 to 30 minutes for them to come.
You are on your own!
Notice in hurricanes and riots, the officials say they cannot do anything and will not come? They are not suicidal (and I don't blame them.)
You are on your own and always have been.
The only question is, have you thought ahead as to what you can do (or would like to train so you can do.) Are you good at first aid? Are you good with your hands and feet? Are you good with a reasonable weapon (knife, gun, stick?) Do you know how to operate machinery (besides the remote?) Do you know how to identify different types of fire extinguishers and how to operate (PASS any one?)
Besides being in our companys HAZMAT team, I'm also CPR and First aid certified. PADI divemaster, expert or above in IDPA, 5th dan TKD. Graduate from over 10 shooting/SD schools. Driven school busses on down to motorcycles. I also know how to use a remote
It's not a brag, it's something I feel strongly about. I feel every good man, and many a woman, should have such skills and more. And most importantly, guts to use them when needed.
Now as for the people who stopped the robbery, I say excellent. It's a risk, but life is a risk. I can tell you from my own experince that such as what they had happen in front of them happens fast and unexpected. You have to react quickly and with some confidence in your skills.
They steped foward when it counted. And that means something.
Or as Robert Heinlein said, "It may be better to be a live jackal than a dead lion, but it is better still to be a live lion.
And usually easier."
Deaf