I think Sheriff Beauchamp was right when he said his #1 suspect was DC,( the guy with the shipping container). (per mtrooper). There is just no way to search his property without him doing something wrong.
I also feel this is why the dog stayed alive so long. DC, was feeding her! He couldn't exactly take her home, in case the sheriff stopped by!
I agree about the dog.
But... motive? I mean- why, you know? Madyson?
That thought scares the bejeesus out of me, truthfully.