The Skeleton Mob at one point in the morning froze, didn't attack and stood there.

So, I was just testing out the cool snapshot 15w41b, I began by testing out the Skeletons' new AI, at first when I went into survival mode, a skeleton fired at another skeleton by accident and so they began fighting. One of them won so I just moved on and saw another skeleton with some zombies. I killed those zombies and the skeleton was just gazing away in the distance, with his bow in the snapshot below. When I tried to push him, he pushed me back and stood in that same spot.