The actors were never given the script in its entirety so none of them knew of their character's fates, sometimes not until the day they were actually filming their scenes. This meant that the actors were - more often than not - stressed, nervous and apprehensive on the day of filming, ideal qualities for the film itself. See more

Goofs

Near the end when Angela and Pablo are listening to the recorder in the penthouse, Angela is obviously rewinding the tape. However, the second time when she rewinds the tape, the audio implies that it was fast-forwarded, as the recording is a diary describing events in chronological order. Watch the tape reel when she rewinds the tape. As it plays forward the reel turns more times than it was rewound. It is impossible for her to hear very much different dialogue without rewinding the tape much more than she does, and then it wouldn't make sense as the dialogue is chronological. In reality, she would be hearing the same spoken passage repeatedly. See more