California - At What Point Does The 21 Day Window Start Regarding A Landlord Having To Refund A Security Deposit Or Account For Its Use, To A Tenant Who Burns Their Apartment Down?

I own an apartment building in which a fire destroyed an apartment.

An investigation report revealed the cause was due to the presence of eight electric bicycles in the apartment belonging to the tenant. The tenant was charging them all at the same time and their lithium batteries caught fire. In turn, the batteries set fire to the apartment, totally destroying it. Water damage from the fire department damaged a second apartment as well. The investigation report specifically stated the building's /electrical system was not the cause. Instead the fire was solely the result of activities conducted/materials maintained by the tenant in the apartment.

The insurance company is low balling me and paying far less then what I am advised the cost of repairs will be (but dealing with this issue is a matter for another discussion). Estimates have been slowly trickling in from various contractor and are not totaled up as to the exact price. Rehab is expected to take three months or more.

The tenant has been taking their sweet time at removing all their property and just got everything out they wanted about 9 days ago. They left the rest to be removed by me, at my expense during demolition. They gave verbal notice they would be looking for a new residence about three days ago.

It will be a while until I get all the repair estimates in, or at least enough estimates to show repair costs will exceed insurance payments, in order to justify withholding the tenant's security deposit. The problem here is time.

State law says I have to either refund the tenant's security deposit or give them an accounting of its use within 21 days of termination, or pay them a penalty that is triple the amount of their security deposit. However, given these circumstances I'm not sure when, or if the 21 day clock has even started. Did it start the minute the fire rendered the apartment uninhabitable, or the day they removed that part of their belongings they wanted to keep (but left the rest) or the day they verbally said they were looking for another place to live (if that constitutes notice of termination within the meaning of the law), or has it not started at all because the property the tenants don't want is still on the premises?

I need as much time as possible to get these estimates together.

Your thoughts?