Board Thread:WARNING ALL USERS False Info\Spoilers/@comment-72.192.213.236-20130731051823/@comment-76.17.53.123-20130731090337

Because Derek did kill her. He snapped her neck while they were under the tree.

As for Peter, we don't know. It could be because of Paige, which I personally doubt, or something from "his past" like Jeff said.

And it's not really a "triangle" but I get what you're saying.