Security Deposit

[Chis Alexander]

We had a customer break his lease 6 months early. He sent us a text letting us know that he found a bigger place and planned to move. We found a new tenant before he moved and rented the office at a higher rate. He stated that we could keep his security deposit because he broke the lease. We've estimated approximately 50% of his security deposit will go towards repairs, removing furniture, management fees and rekeying. Since he broke the lease, are we still obligated to send him the remaining amount of the security deposit and a letter confirming our intentions?