California 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.
So the use of deadly force may be justifiable when necessary to resist the attempt to commit a forcible and life-threatening crime, provided that a reasonable person in the same or similar situation would believe that -
(a) the person killed intended to commit a forcible and life-threatening crime;
(b) there was imminent danger of such crime being accomplished; and
(c) the person acted under the belief that such force was necessary to save himself or herself or another from death or a forcible and life-threatening crime.
The guy in the original post robbed the person and was attempting to flee... it appears California Law would allow shooting to stop him... that being it was a felony and he was attempting to apprehend the person for the felony commited.