LL Refuses to Return Security Deposit

[kimchimonster]

My father has rented a small store in the bronx for 25 years. His lease recently ended and now his LL is forcing him to shut down his business. My father requested that his security be returned, but the new LL has ridiculously claimed that he only has $100 deposited. We have most of the reciepts to prove that he owes about $2500+ . But some of the reciepts are missing from our house since it's hard to keep track of 25 years. Is it my responsibility to prove our security deposit , or the old Landlord's, or the new landlord's? WHat can I do?! I'm stressing over the sake of my father's business. I would appreciate any help you could offer. You can contact me on AIM at : kimchimonster or email me at kimchimonster@aol.com THanks so much.
Chunwoo