Legal Question in Criminal Law in California

There is the theory of "defense of others." You are entitled to use as much force as the person actually in harm's way is entitled to use to protect themselves.

For example, if you see person Y yelling at person Z and poking them in the chest with their finger, you can't shoot them under the theory of defense of others. It's clearly excessive force. You *may* be entitled to shove person Y out of the way to stop the assault/battery on person Z. That's about as much force as Z could have used.

In your scenario, if person Z was entitled to use deadly force to stop an imminent threat of actual bodily harm or death, then you are allowed to "step in the shoes" of person Z and use the same amount of force.

The problem with "defense of others" is that you may never really know what was going on between Y and Z. What if Y and Z were practicing for a play and there was no harm? What if Z had just robbed Y, but Y got the gun away from them and was holding Y until the police arrived.

That's just a general overview of the theory of self-defense and defense of others. It in no way in intended to be legal advice. It was offered for general information only and you should not rely on it, act upon it, do a particular course of conduct or use any force or weapon based on it. The bottom line: Your actions are your responsibility and will be analyzed under the law applicable to your situation. The above answer was not intended to create a legal defense for you in a future situation. I wash my hands of this.