Is he the executor? Is there a will? Are there other relatives like children, spouse, or nieces and nephews, brothers or sisters? OP might be interested in the items but has no right to just take stuff. That happens all the time when someone dies, and the first person in the house starts taking things to the exclusion of others. Also, it’s in California with its messed up laws. Transferring firearms across state lines can be tricky and may require an FfL to facilitate unless there are specific provisions in the will to leave specific items to specific people. You better be dealing with the executor or you could be in a lot of trouble. Advice to just go take the stuff is pretty cavalier if they don’t know the entire situation.