The conduct you describe could be charged by the DA in several ways. If there was a verbal threat, they could file Penal Code section 422 - criminal threats. That carries up to 3 years in prison and is a strike. They can add on enhancements for the use of the firearm during the commission of that offense, adding time.
If they can prove the gun was loaded, they may file assault with a firearm - 245(a)(2) - another strike, carrying up to 4 years in prison.
Or it could be a misdemeanor brandishing - Penal Code section 417 - 3 month minimum, 1 year county jail maximum.
He could also face additional charges for the possession of the firearm on the different day.
The details matter. It could be a huge range of charges. What happens depends on the charges, the judge, the DA and to some extent, his attorney.