Night of the Headless Horseman - S3-E11
Visible crew/equipment: When Nate and Dorian fight at the bar they are replaced with obvious stunt doubles with totally different hairstyles.
Night of the Headless Horseman - S3-E11
Visible crew/equipment: When Jessica arrives at the station and Dorian opens the car door, stage lighting screens are reflected on the glass.
Night of the Headless Horseman - S3-E11
Visible crew/equipment: When Nate Findley rides his horse the actor's stunt is very noticeable in the wide shots.
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.