I imagine contracting with an elder, especially if you are a lowly congregant, is fraught with peril. The unwritten, unspoken rule that you don't actually have any legal recourse if things go pear-shaped must be always be at the back of one's mind in those situations.
As to the murder, let's not get distracted by the JW aspect of it. These cases happen from time to time but prove nothing except anecdotally. Such things can happen in any situation involving an unequal power dynamic.
It's upsetting to see anyone murdered (or otherwise abused) by someone they thought they could trust.