Let's put it this way: if someone threatens ME with grave bodily injury, I'm going to respond whether or not I'm on duty as an EMS provider. I have been trained to respond with an appropriate level of force in an appropriate manner.
You don't have to be taking fire to respond with lethal force. So, yes, there are situations where I would potentially shoot first even if I wasn't being shot at. I will not elaborate on any further on that. If you've been trained in use of force, you'll know what's legal, and you'll have training to back up your response.
Remember, the best way to avoid a fight is to not be there...
This subject is everywhere on the internet and I'm pretty sure it can be debated indefinitely
. But I agree with akulakawk and so does the law (in my state).
The are certain criteria that allow for "justified homicide", such as someone entering my home illegally and me fearing for my life or my families. This also applies if you have a CCW and are attacked on the street. If you decide you want to pull the gun and shoot, you must be 100% prepared to be treated and tried as a criminal, so you must be 100% convinced that you are mortally in danger. The best way I heard it described is that if you even consider not doing it then you shouldn't.
Here's the criteria for CA:
Penal Code 197
Homicide is also justifiable when committed by any person in any of the following cases:
1. When resisting any attempt to murder any person, or to commit a felony, or to do some great bodily injury upon any person; or,
2. When committed in defense of habitation, property, or person, against one who manifestly intends or endeavors, by violence or surprise, to commit a felony, or against one who manifestly intends and endeavors, in a violent, riotous or tumultuous manner, to enter the habitation of another for the purpose of offering violence to any person therein; or,
3. When committed in the lawful defense of such person, or of a wife or husband, parent, child, master, mistress, or servant of such person, when there is reasonable ground to apprehend a design to commit a felony or to do some great bodily injury, and imminent danger of such design being accomplished; but such person, or the person in whose behalf the defense was made, if he was the assailant or engaged in mutual combat, must really and in good faith have endeavored to decline any further struggle before the homicide was committed; or,
4. When necessarily committed in attempting, by lawful ways and means, to apprehend any person for any felony committed, or in lawfully suppressing any riot, or in lawfully keeping and preserving the peace.
Penal Code 198
A bare fear of the commission of any of the offenses mentioned in subdivisions 2 and 3 of Section 197, to prevent which homicide may be lawfully committed, is not sufficient to justify it. But the circumstances must be sufficient to excite the fears of a reasonable person, and the party killing must have acted under the influence of such fears alone.
Penal Code 198.5
Any person using force intended or likely to cause death or great bodily injury within his or her residence shall be presumed to have held a reasonable fear of imminent peril of death or great bodily injury to self, family, or a member of the household when that force is used against another person, not a member of the family or household, who unlawfully and forcibly enters or has unlawfully and forcibly entered the residence and the person using the force knew or had reason to believe that an unlawful and forcible entry occurred.