Legal Question in Real Estate Law in Nevada

It could depend on what the charges are for. Generally, the owner is responsible for everything related to the property, and the security deposit is collected in the hope that it will be sufficient to cover all expenses when the tenant moves out. If there are more expenses than deposit, then the owner usually has to make up the difference. One exception might be if the manager made an error or otherwise overpaid for unnecessary services. Then, it would be hard for him to argue that you should bear the burden of his screw up.

As for the manager suing the tenants, it is likely he is suing in your behalf, so if he is successful in collecting the unpaid balance, the money would go to you as reimbursement of what you had to pay. If you pay the shortages of expenses, you are the damaged party (by the tenant) and deserve compensation for your damages.