Why you must watch this movie about one of the most horrific moments in TV history

Ten years ago, when Robert Greene learned the story of Christine Chubbuck - a 1970s TV reporter in Sarasota, Florida, who was the first person to commit suicide on live television - two things instantly came to him: "How do you make a film about someone who kills themselves?" and "I need to see the footage."

With the most mundane moments of our lives now captured and immediately put online for the world to see, Greene was shocked to find that not only was no footage of the Chubbuck suicide online, but there was no video of the reporter period.

"She went on television to commit suicide so people would see it, and that has been lost," Greene told Business Insider. "There's such pathetic irony to that."

As the years passed and Greene began making movies that walked the line between nonfiction and fiction - like 2012's "Fake It So Real," which looks at the independent professional-wrestling circuit, and 2014's "Actress," an intimate study of character actress Brandy Burre ("The Wire") - Greene couldn't escape the Chubbuck story.

With Chubbuck essentially a pre-internet folk story - as years had passed since Greene learned of the suicide and the footage of the suicide still hadn't surfaced - he decided to start the Chubbuck project, but with a unique angle.

"I never wanted to make a straightforward story," Greene said. "The title of the movie actually became the full idea."

"Kate Plays Christine," which opens in select theaters Tuesday and premiered earlier this year at the Sundance Film Festival amid much conversation about it, is a part documentary, part fictionalized narrative that explores Chubbuck through actress Kate Lyn Sheil ("House of Cards," "The Girlfriend Experience"), who plays Chubbuck in scripted scenes depicting key moments leading up to her death while also chronicling Sheil's journey in Sarasota by talking to people who knew Chubbuck.

Greene captures the similarities between the women - Chubbuck's frustrations about not being taken seriously as a journalist in a male-dominated industry; Sheil's concerns about being pigeonholed into one type of character - while also delving into Sheil's struggles to truthfully represent Chubbuck in the scripted scenes with little to no source material. (Sheil is actually not the only actress to play Chubbuck in a Sundance movie; Rebecca Hall plays her in the film "Christine," which opens in theaters in October.)

"Kate is the film," Greene said. "Kate is someone I'm friends with but also someone I find very interesting to watch on-screen because I don't know where things come from, and as a documentary filmmaker, I'm fascinated by that."

Sheil acknowledges, however, that her performance is not without some dramatics for the camera.

"It's simultaneously genuine and completely fabricated," Sheil told Business Insider of her performance in the film. "It's me knowing what Robert was trying to do, being frustrated by that, but playing it up."

For example, in one scene, Sheil tries to do one of the scripted scenes but stops and tells Greene it's not working. When one of her costars gives her encouragement, Sheil lashes out at her. Asked how real that scene was, Sheil acknowledged she would never talk to another actor that way in real life.

But that aspect of performing for the camera was something Greene wanted to explore in the film, since many documentaries are not as authentically "real" as we may think.

"If you have a camera, you have a performance - that's just a fact," Greene said. "Most documentaries are so eager to hide that because authenticity is this gift to the audience: 'I didn't make this up.' But it's a film - it's not reality. One of the things we're trying to do in the film is to take that as a starting point, not an endpoint."

And then there was the ending of the movie. Did the filmmakers want to reenact a suicide? What of substance would it give the audience?

Greene and Sheil said they didn't come up with the film's ending until the night before they shot it.

"I didn't want to pull the trigger, but flying down to Florida, the plan was to reenact the suicide," Sheil said.

Going back and forth with ideas, the two, along with cinematographer Sean Price Williams, finally landed on an ending they all agreed on (the ending was filmed on the 41st anniversary of Chubbuck's suicide), which was greatly influenced by a discovery they made in the reporting for the movie.

"The ending to me is everything I care about in movies," Greene said. "The way it came about was a very documentary way. We have a scene and we've talked to people, and now it's an absolute collision of fiction and nonfiction."

A melodrama wrapped in an investigative documentary, "Kate Plays Christine" is a unique story that explores depression, female stereotypes, and privacy in a time when all-access is the norm.

It's a movie that will leave you with more questions than answers, and Greene wouldn't have it any other way.

"The point of the movie is this is what it takes to tell this story," he said. "So when the audience is asking, 'Is it real?' - 'Is Kate deciding to do that, or did Robert tell her to do that?' - we're inviting those thoughts because most films don't invite those thoughts, and it's fruitful because I think that is the nature of the Christine Chubbuck story."