the unsolicited emails were about to get downright frightening. and soon, and sherry detectives had a new mystery on their hands. coming up -- another cold blooded killing. >> shot execution style. >> with a bullet in the back of the head? >> yes. >> they walked in, fired the shot, walked out again. >> that's what it seems to be. >> and another dark tale about to unfold. >> how many murders can you have in one family? >> when "dateline" continuous. every emergen-c gives you a potent blend of nutrients so you can emerge your best with emergen-c.