(1) Subject to the provisions of this section and of section 28-1414, the use of force upon or toward the person of another is justifiable to protect a third person when:
(a) The actor would be justified under section 28-1409 in using such force to protect himself against the injury he believes to be threatened to the person whom he seeks to protect;
(b) Under the circumstances as the actor believes them to be, the person whom he seeks to protect would be justified in using such protective force; and
(c) The actor believes that his intervention is necessary for the protection of such other person.
(2) Notwithstanding subsection (1) of this section:
(a) When the actor would be obliged under section 28-1409 to retreat, to surrender the possession of a thing or to comply with a demand before using force in self-protection, he shall not be obliged to do so before using force for the protection of another person, unless he knows that he can thereby secure the complete safety of such other person;
(b) When the person whom the actor seeks to protect would be obliged under section 28-1409 to retreat, to surrender the possession of a thing or to comply with a demand if he knew that he could obtain complete safety by so doing, the actor is obliged to try to cause him to do so before using force in his protection if the actor knows that he can obtain complete safety in that way; and
(c) Neither the actor nor the person whom he seeks to protect is obliged to retreat when in the other's dwelling or place of work to any greater extent than in his own.