I think the answer rests in the definition of "brandish": transitive verb
1: to shake or wave (as a weapon) menacingly
2: to exhibit in an ostentatious or aggressive manner
To brandish is not to defend or to ward off an aggressor. It is true; do not pull your weapon unprepared to use it, but if the threat of use reverses the aggressor, deadly force is no longer deemed appropriate, albeit one would probably prevail if one did fire, as the threat did exsist. No doubt it would be a split second decision, and it should be reported right away, as the previous writer indicated, so you get the report right first!