Over the course of the run of the Sopranos, their has been many times when Tony Soprano has been humanized; However, tonight was the return to evil Tony. He killed his once air apparent Christopher when he had the chance because Christopher had become a liability. It fits into the general show pattern of random death and major death like Ralphie, Big Pussy, Tony B being at the hands of Tony himself. (on a side note, it was great foreshadowing and a homage to The Departed by having Christopher put in the soundtrack right before he died.) It also should be noted that A.J. is slowly turning into his cold hearted father and has become the air apparent by default.