Murder to a Jazz Beat - S1-E13
Continuity mistake: Jessica and Jonathan sit down to chat; he says, "Tastes and smells... worthy of kings and their consorts," and raises his hands. An instant cut later, from a different angle, they're lowered. (00:04:49)
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.