Seeking advice on a Baltimore rental

[Sam Sharata]

I just closed on my first Baltimore investment rental this past Friday (8/19/2016). It was an all cash purchase with a tenant already in place, and after I signed and submitted payment, the seller informed me that the tenant has not yet paid the rent for August and is not responding to his texts and phone messages.

The lease was signed in May, 2016, and according to all paperwork, the tenant has a stable job. The rent is typically due by the 9th which they have paid on time for May, June, and July. 

The tenant was provided with the right of first refusal, so they are aware of the imminent sale of the property. 

The seller/prior landlord said he submitted a Failure to Pay Rent complaint with the District Court, and has proposed to prorate his portion of the August rent from the security deposit and provide me with the remaining balance as payment of the security deposit and my share of the rent for August. 

I don't agree with the idea of prorating the rent and taking it out of the security deposit, and am frankly at an impasse on how best to proceed with this matter. Has anyone ever encountered this issue? If so, what did you do to resolve it? Please help!