I don't think the affadavit makes it clear that Alex was the killer. Lori could have drugged Tylee (to death) or Chad could have shot her. I think there has to be some reason he made the excuse of shooting a raccoon (one shot, I'm so awesome!
). Either Chad dealt her the final death blow on the property, or he had some story about needing to shoot a zombie to be sure it was dead, or perhaps he just fired a shot on his property to keep up the "alibi" of the raccoon burial. They'd shot CV, and would also attempt to shoot BB and TD.
I'm really hoping that JJs remains being mostly intact will bring the evidence that LE really needs to lock in the COD for all of these people. Since they've been so "sloppy", I think using the same methods/poisons totally fits their MO.