Derek Hamilton who plays Detective Elliot was the first person cast in the movie. Director Chris Fisher had previously worked with him in a movie he wrote and produced called Taboo. Casted him because since this was his first time directing, he wanted someone he was comfortable with who knew him and what he was going for. In fact Derek was hired while the script was still being written, and even helped with his character's development.
Bret Roberts who plays the Nightstalker was also cast early. Director Chris Fisher met him in 2000 at the Sundance Film Festival. He was passed out on Chris's couch in the middle of the afternoon. Chris didn't know who he was, so he shook him and asked. The two ended up becoming good friends. And Chris cast Bret because of his resemblance to Richard Ramirez. Who's story the film is based on.
After Lieutenant Mayberry talks to the press, and walks back into the police station with Dectective Elliot and Gabriella. He is mad at the snotty reporter so he throws a tantrum. This was ad-libbed by actor Evan Parke.