Visible crew/equipment: When Frank is put in jail and the camera moves around the iron bars, the camera's moving shadow can be faintly seen on the column.
Visible crew/equipment: When the episode ends and the sheriff laughs, a large lighting screen is reflected in his right lens.
Visible crew/equipment: When Marcia gets back into the car, a boom-mic operator is reflected in the door.
Visible crew/equipment: When the episode begins and Jessica recounts the story, several set lights are reflected on the coffee pot.
Answer: In a flashback scene, it was shown that he had a violent temper, so it stands to reason that he finally killed her in a fit of rage.