The actions taken could vari from just telling at him them to back off to drawing and firing with out warning. One needs to be prepared to use the right tactics for the right situation.
It is easy to be a Monday morning quarterback. I see way to many comments of shoot first ask questions later. Such thinking could easily end with you in prison.
Using force that result's in the death or servre injury of another person needs to be taken only when justifiable.
There is nothing wrong with a person defending themselves but doing so wrongly will make your life miserable for a long time.
Too many people are willing to draw, but are not willing to shoot. Those are the ones that go home in a body bag.