Law of Defense of Others: Defense of Family v. Strangers v Active Shootings

Generally speaking, we're allowed to defend other people largely to the same extent we are allowed to defend ourselves (or they would be allowed to defend themselves). That said, there are some subtle but IMPORTANT distinctions in how this straightforward defense of others law is applied when acting in defense of family & friends versus in defense of strangers versus defense of innocents in an active shooter scenario. Do you know these differences? If not, SHOULDN'T you? NEW...