You don't know that, and neither did he. He was just afraid, and too stupid in his petrification to wait and see what happened.

If I had changed, then I would arguably have already been dead, would I not? And even if I were to try to kill anyone, all of you were younger and faster than I am. I've no doubt I could have been stopped.

There's every chance in the world that I wouldn't have changed at all.