From the Horse's Mouth - S7-E16
Continuity mistake: Christie is holding the phone in her left hand. In the very next cut, she is suddenly holding it with both hands. (00:16:32)
From the Horse's Mouth - S7-E16
Revealing mistake: When Christy and Jessica drive to the stables, Jessica is briefly replaced by a younger stand-in who bears little resemblance to her.
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.