First tenant just left without notice and destroyed the place

[Eva Rosales]

So, I help my dad who lives out of the country manage a duplex that he recently bought. This is our first round of tenants, we have one side rented, that *knock on wood* seem great. We screened a lot of tenants and waited for a great one and really thought we found them for the other side....Younger married couple with a baby, recently discharged from the navy, great rental history, income/employment, credit score, he had two puppies which he paid extra for monthly, they seemed upstanding and silly me had a great feeling about them.  They moved from out of state to here in Texas, and a few weeks prior I had a skype meeting with them to show them the property, they came and loved it, moved in the next day. They've been in for a few months and paid their rent on time, there wasn't any issues. Yesterday, I get a call from the tenant next door asking me when the unit is going to be for rent because he saw them move out and he had a friend he wanted to move in. I checked our rent payment online portal and show they haven't paid their rent and late charges were starting, so I texted the tenant and told him late charges were incurring and I heard that he has moved out, but I did not receive a notice of vacancy, is this true, he calls me immediately and said yes, he moved out, it got too expensive and that he's sorry for the inconvenience and he can pay for this month's rent in installments if that helps, I didn't agree to that, but didn't say no. I told him I'll need a forwarding address so that we can get a security deposit back to him if needed and he scoffed and told me that he definitely won't be getting his security deposit back. I told him that I would talk to the owner and call him back. Me and my husband went to check on the property that night and the place reeked. Electricity has been off for days, full fridge of food that is rotting, dog poop EVERYWHERE, most of his furniture and garbage is everywhere, baby room still has crib, changing table even a car seat, hell they left their keurig, the only thing we see missing is their tv and clothes--multiple holes in the walls chewed out from the dogs. Looks like they left the dogs there by themselves for a long time. I got more info from the other tenant and he said he saw him just packing clothes without boxes in his car and asked him, and he told them he is moving back to California. I got the electricity turned back on today, and changed the locks. I have a clean up crew coming tonight but talking to my dad, he's worried that since he didn't give us a notice of vacancy in writing, and since most of his stuff is there and he's asking to pay the rest of the month in installments we don't want to be sued if he tries to go back for his stuff. My idea is to email him asking to email us with the date of vacancy to ensure that no further late charges or late charges are added to his account, but I honestly don't know what to do next. , or if I can even have that clean up crew come tonight. Help?