Can we all agree that Peter Hackett killed Shannan?

Personally I think he was at the original party and drugged her there. Like is there a public guest list of that party posted anywhere? I think Rex had nothing to do with this one. And his phone calls sounded like a real good way to cover his tracks. Or maybe just maybe he was scared about dragging her. Maybe a cop found her killed her and then brought phone to Peter to start damage control since he’s the one who drugged her?