Media execs are dropping like flies today: On the heels of the departure of Jonathan Klein from CNN, NBC CEO Jeff Zucker announced on Friday that he’ll be leaving the network. Zucker is NBC’s longest-serving senior manager; he says his decision to leave was “incredibly emotional’ and “gut-wrenching in the sense that you have spent your whole life here at NBC.” His decision to leave comes as no surprise, as everyone said his number was up when Comcast took over the network. In his goodbye message, he acknowledged mistakes at NBC Entertainment, particularly with regards to the Jay Leno-Conan O’Brien fiasco. “Do I wish we’d had more success at NBC Entertainment in recent years? Yes, of course.” Meanwhile, over at CNN, Klein will be replaced by Ken Jautz, the head of Headline News.