The angle emerge I've seen, from what Kevin Sullivan said Nancy had a crazy side too, she stabbed him. So it's possible Nancy and Chris had a huge fight, what if Nancy had tried stab him or threatened to shoot him? I'm not saying that's the case but Kevin Sullivan's information shows she has a crazy side, her sister also hinted at it. Maybe Chris and Nancy had a huge fight and Daniel was somewhat of a mercy killing, especially as he was sedated prior. It was probably a combination of things including brain damage. Sullivan also said he heard Benoit was having an affair. Nancy was known not to take shyt, maybe she lost it and was trying to kill him or and he snapped or it got out of hand. What would happen if Nancy tried to stab Chris? He was a pretty extreme guy, particularly in the mental strate he was in. Another theory is she threatened to kill Daniel and Benoit lost it, and Daniel was a mercy killing. This is all spectialtion but Sullivan's info introduce a new element into it, because it shows Nancy had a wild crazy and violent side too if it's true too.