An Heir Has Died Before Probate Distribution. What Documents Do I Need To File With Court In California?

I feel like the answer to this should be simpler. Due to the size of the estate, I am handling this on my own and have been able to find most answers I need.

Sadly, one of the intestate heirs has died before probate could be completed. What do I need to file with the courts to establish this fact? Do I need to file a death certificate?

I assume I also need to file a court order that names the person who is the administrator of the heir's estate?

Is this information written down anywhere, or is there just a general procedure for establishing new facts about the probate process?