You’re justified in many cases using a firearm to defend yourself even if the other person does not have one. Knives, clubs, disparity of force due to age or infirmity. Somebody gets the better of you into a fight and is choking you into unconsciousness. There is no legal concept that somebody else must fire first before you can discharge a firearm in self-defense.
A 6’8” biker that’s built like a linebacker continuing to advance when told to stop is good enough for me.
Disparity of Force is a legal concept that supports this.
or Treyvon banging your head against the cement