Funeral at Fifty-Mile - S1-E22
Other mistake: It's a clear day not a stormy night as it should be when showing the barn in the flashback. Look closely and you can see a clear sky through the barn walls cracks.
Funeral at Fifty-Mile - S1-E22
Other mistake: In the end credits, Jesús is misspelled Hay-Soos, phonetically.
Mirror, Mirror, On the Wall (2) - S5-E22
Other mistake: When the sheriff finds the apple, the bitten side has a fresh white colour, instead of the brown colour it should have after the many hours passed.
Other mistake: During the opening credits, a passenger on the streetcar can be seen waving directly at the camera.
Other mistake: Following the accusation against the sheriff, the confrontation between the Mayor and Jessica is marred by a visible technical glitch. A negative-style overlay runs through the scene, including a light flare above the Mayor's head, a thick black line across the frame, and a whiteboard intermittently superimposed over the image.
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.