In the dinner party scene, Jack Landsford, played by Tom Berenger, arrives at the party with slightly shorter hair than when he leaves. When he enters, his hair is trimmed tighter to his head, while when he leaves, his hair is definitely a tad longer on the sides, back, and bangs, enough to notice that this much hair would not grow in a matter of hours. This scene likely had a re-shoot.
When Carly and Jack wrestle for the revolver, his hand is holding the body of the revolver and the cylinder when he is shot. The hammer cannot be pulled back, and the trigger cannot be pulled, if the cylinder of a revolver is locked in place. It cannot be fired.
Following Gus Hale's death, Carly finds a newspaper clip whose title is "Horror high rise claims third victim". Gus was the third, Naomi Singer was the second, but it is not revealed who was the first.