Legal Question in Criminal Law in California

From what you wrote (and just based on that), he sounds like he has a good self defense argument.

And because you're writing base on third hand knowledge, the best I can offer is that he needs an attorney to hear out the whole story and defend him.

He is probably facing a felony charge with years in prison if convicted. The only advice that is worth anything is for him to get legal counsel who knows how and what to do to best represent him, using whatever credible facts and evidence there is for motions and defenses at trial, if necessary. The risk of loss at trial is mandatory sentencing to the full term provided in the law upon conviction. The attorney's job is to get a good 'deal' you can live with, or prepare for trial. If serious about hiring counsel to help in this, and if this is in SoCal courts, feel free to contact me.