The wolf closest to me, the reddish brown one, turned its head… It gazed at me… the deep eyes seeming too intelligent for a wild animal. As it stared at me, I suddenly thought of Jacob. (10.174-176)
Although Jacob has transformed, his essence or identity still lives within his werewolf body.
[Jacob to Bella:] "When I… changed, it was the most… horrible, the most terrifying thing I’ve ever been through… there were voices there, in my head, telling me what had happened and what I had to do. That kept me from losing my mind." (13.224)
At first Jacob experienced his change as terrifying, but then the voices in his head told him that he didn’t have to be afraid, because he’d met his calling and he accepted it.
Paul seemed to fall forward vibrating violently. Halfway to the ground, there was a loud ripping noise, and the boy exploded. (14.19)
It’s the common saying, "I’m going to explode of anger," transformed into a supernatural, visual representation.