This is just one man's opinion but "carrying" a concealed weapon offers us no protection at all. It is the understanding that we may be placed in the terrible situation where the taking of another's life can occur and our willingness to do so if it does get to that point. Hopefully that burden has been considered by everyone who carries a weapon. I carry a weapon because I've accepted the burden of being willing, if necessary, to use it.
We are not LEO's and we have no obligation to stop a crime in progress but California law allows use of deadly force and homicide (literally the killing of a human) in several instances. Since a holstered weapon worn on the body can't "reasonably" be used in the situations originally posted, drawing the weapon would not be brandishing but would be a logical step between observing and intervening.
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.