Forgive me if this has been pointed out already.

So my wife and I have been going back and forth about whether Charles or Sazz was the real target, when Sazz was shot in Charles's kitchen. Generally my position was that it was dark, Sazz was dressed like Charles, and generally if you were aiming a gun at someone's apartment, it's because you want to shoot that person, and not someone else. When someone with Charles's silhouette walked into Charles's apartment, the killer shot them because they thought it was Charles.

But the killer has had cameras in everyone's apartment, including Oliver's, and could well have seen and heard Sazz, at the Death Rattle Dazzle after-party at Oliver's apartment, tell Charles that she would go get the Malbec. And if they wanted to kill Sazz (for whatever reason), they could then have decided to take that opportunity to shoot her, knowing that when a Charles-shaped person entered Charles's apartment a few minutes later, it was in fact Sazz. (The killer would presumably also still be able to see Charles on one of the cameras in Oliver's apartment, to verify that it was Sazz entering Charles's apartment.)