Tenant possibly lying to get out early??

[Mark Hu]

We have a tenant who gave us 30 day notice August 15. He 'conned' my mother into saying it was okay to move out on the 5th of this month, saying he could sign another lease early, my mom was confused about the move out date.
This tenant is a habitual liar and probably didn't even sign a lease. I am very angry but am not sure how far I should go in fighting this guy? What do you guys think?