40/ca I Found My Landlord Dead! What Do I Do?

This is written on behalf of my friend A, living with his landlord S in San Diego California. Two months ago, he found his landlord dead. S was older, passed from natural causes. He’s been living with S on a month to month lease for about 6 years. No will has been located and the house is likely going to probate. The family of S lives in Ohio, and is being extremely aggressive about trying to force A out of the house. They’re threatening him, demanding access to the home when he isn’t there.

The family of S has not provided a deed to the home, but they’ve aquired keys to the location from S’s ex husband and are invading the house. What are A’s rights here in this situation?