9to5

Caleb, the ghost, was killed by his brother Phillip, the guy getting scared. His wife informed him that if he was happy, he wouldn't be able to stay, so instead, he is haunting his killer as a vengeful spirit. But humorously, it is depicted as a bland and boring job.

Oddly enough, this kind of contradicts everything we've seen about ghosts so far in these comics. For example, Luz's dad watching over her. That or Evelyn (the wife) is just wrong in what she told Caleb.