Clay became plagued by anxiety attacks and frequently saw hallucinations of Bryce and Monty, later learning he was suffering from what his therapist labeled dissociative episodes. In Episode 8, we learn that Clay manifested a sort of alter ego, one who ran around creating chaos while Clay was in a fugue state.

Is Clay a hallucinating Monty?

While Clay waits for Tyler, who is being questioned by police at the station, Clay starts to hallucinate, seeing Monty shaking his car and intimidating him. This isn't the only time Clay hallucinates, as he sees Monty at school in the faces of the football team.

Is Clay hallucinating the phone calls?

As Clay approaches the dummy he begins to hallucinate and sees Monty in place of the dummy. He has a panic attack. This is when Diego and his friends arrive on the football field revealing themselves as the mystery callers. The calls stop thereafter and they reveal that it was just a prank.