security deposit deductions letter

[Linda Thomas]

Hi there.,

Two tenants on the lease. Tenant 1 moved out. Tenant 2 stays. 5 months goes by to come to find out that now tenant 2 moved out without our knowledge and let squatters move in.. had to file for eviction, got them out finally. Over 4k in damages, utilities, past due rent, court fees, tons of trash, holes in walls, pee everywhere, etc. 

Now, tenant 1 texted me asking when he was going to get the sec dep back. I explained the process and how I have 30 days to either send check or itemized letter with deductions. Tenant then proceeded to provide me with his new address and another address for tenant 2. 

Question. 

do you send the itemized letter certified mail to both of the new addresses he gave me? Or to just his since I have not had any communication with the other tenant that was on the lease? How do I know this other address is even valid? Or if they split up etc?

do I also send a copy for the sec Dep letter to the rental ? 

Cover my basis and send to the rental and the 2 addresses the one tenant provided via text? 

How would you handle this? best way possible? 

thank you!