Even though this is actually on the second disc of David Fincher's excellent "Zodiac" film, I decided to give it a unique review, since it's basically a second movie - a feature-length documentary about the Zodiac killings featuring interviews with the real-life participants and archival footage and photos.
This documentary, featuring the real photos and people, is somehow even more frightening than Fincher's film. There is a wealth of interview footage from policemen, people who knew the victims, and old news footage to tell the story of the killings.
The interview subjects are presented simply, head and shoulders talking in front of a plain white background. Some of them can be a little difficult to understand, either due to their advancing age (considering the case goes back to the 1960s) or because of injuries (Michael Mageau was shot multiple times, including through the face, which has left him with a speech impediment).
There's a wealth of information on display here, probably more than is necessary, but it makes it a particularly comprehensive documentary on the subject. The personal stories told are frightening and sad as people recount what essentially became the some of the worst times of their lives. Mageau's recount of the night he survived and his girlfriend Darlene was killed is fairly intense, despite his speaking problems. He talks about how much he loved her, and how he planned to marry her. The responding officer caps it off by talking in detail about how the girl was still responsive when he arrived on the scene.
This documentary is so in-depth, we even hear from the police phone operator in Vallejo the night Mageau was shot. She recounts the night she received a creepy phone call from the killer, who took responsibility for both that shooting and a double murder the previous year in another town. She also mentions that she can still hear his voice in her head, still gets the chills.
It's these kinds of stories that take what could easily have been a very rote true crime documentary and makes it just as effective and intriguing as the fictionalized version. Each of the killings is examined in detail, but it never gets boring. The police and investigators could be very dry and technical, but the emotional impact of working on these cases comes through, drawing in the audience beyond just the details.
I can't recommend "Zodiac" and this companion documentary enough. If you're interested at all in these kinds of cases, this is a fantastic one-two punch of Hollywood crime drama and real life.