Kennesaw must have [Major Spoiler]

killed Elizabeth, and Wayland did as he confesses, that he discovered her body, cut her up and disposed of it (and Kennesaw wanted Wayland to die from ingesting the poison pills or so he thought)

OR

was in on Wayland's fake death (as Wayland's responsible for Elizabeth's murder and dismemberment) because he took the bottle of pills off the water cooler and slipped it into his pocket. Why else would he do that? It should have been bagged as evidence.

Maybe, Kennesaw was bought like all the others but was surprised/shocked when Wayland produced the tape. Wayland then made good by confessing but not to her murder which alarmed Kennesaw as it still places him in the frame.

*scratches head*

The ending kind of clears it up that Wayland may be a serial killer, but Kennesaw hiding the pills just leaves me wondering.