Continuity mistake: Earlier in the movie, we can see in the elevator that 16 is the highest number floor before the Penthouse (PH). Since they live in a two-story Penthouse, that would mean they are occupying the 17th and 18th (top two) floors of the building. But later in the movie when Mel Gibson hears the shot on the phone and thinks they have just killed his son, he runs out onto his balcony and looks down at the street. He is only about 4 or 5 stories up at this point.