It all depends, I live in a pretty quite neighborhood. I don't "know" everyone around me, but I know who belongs and who doesn't. If it is someone who I recognize they will be let in, the door will be locked behind them, and I will give them aid while waiting for the police and the medical staff to arrive.
If it is someone that is unfamiliar to me, we will just have to play it as I see it then. They might get in they might not. I might exit the house through the garage and assess what is going on then decide what I am going to do.
I would have a hard time living with the fact that I let a person die on my front porch because I was too afraid to give assistance to them, especially if all threats had ceased to exist. By sitting inside you can't really know if there is a threat left or not.
I would have a hard time explaining to my 5 yr old why there was a dead man on my porch, and I just sat and ate popcorn or whatever while he died. That would go against everything I have taught him so far.