Honestly, I actually believe he actually was changing. But, too late late now. He had pissed off the wrong group.
Added: I just have to add this part. I think that the fact that she did it wasn't because of the whole murderer's neurons/drugs deal, but simply because of the fact "she" is a female. Sounds bad, but think about it: one thing about males is they they tend to let things go after a bit, whereas women do tend to hold grudges longer. Can't blame her in this case, but it is just a possibility.