When casting his film, “Munyurangabo,” director Lee Isaac Chung took a leap of faith. He selected only unprofessional actors, local Rwandans that had never performed in front of a camera. The cast never saw a script. And when cameras rolled, the actors improvised every piece of dialogue — in a language Chung did not understand.

“My actors come up with the dialogue themselves so that they can bring forth their own experiences,” says Chung, who heads the production company Almond Tree Films in Brooklyn. “It allows them to bring out more of their own reality rather than having to conform to something that fits an outsider’s ideas or written words.”

“Munyurangabo” chronicles the journeys of two Rwandan teens searching for reconciliation with the horrific consequences of what is known as the fastest genocide in history. Chung, 29, chose to produce his first feature film on post-genocide Rwanda because since 2003, his wife Valerie has spent her summers working as an art therapist for genocide survivors. In 2006, Chung joined his wife’s organization, Youth With a Mission (YWAM), based in the Rwandan capital of Kigali, to teach photography and filmmaking to a group of boys and refugees. He eventually decided to produce “Munyurangabo” as a joint effort with his students.

After casting local actors, including Edouard B. Uwayo, Rwanda’s poet laureate, Chung shot the film in 11 days. “Munyurangabo” uses the Kinyarwanda dialect, and according to Chung, is the first feature film in Rwanda that is entirely scripted in its native language.

Chung’s film has also raised concern, mainly because he is not an African director. “There is a healthy amount of suspicion out there when an outsider is doing something in Africa,” says Chung. “For instance, by making this film, was I being exploitative at all? Was I being irresponsible? Was I bringing in a story of my own without completely understanding the situation in Rwanda?”

Which is why Chung used tactics such as improvisation to allow his actors to inform the film. Before arriving in Rwanda, Chung and his co-writer Samuel Anderson wrote a basic treatment in English. But that summer in Kigali, the script changed dramatically after Chung interviewed orphans and runaways so that their experiences could be incorporated into the story.

The lead characters — a Tutsi orphan and a Hutu runaway — are Ngabo (Jeff Rutagengwa) and Sangwa (Eric Ndorunkundiye), two teenage friends despite coming from the different tribes that warred against each other during the 1994 genocide. It is later revealed that they are en route to an unspecified rural village to kill the man who murdered Ngabo’s father. Along the way, they visit Sangwa’s parents, who haven’t seen their son for three years.

The plotline mirrors the experiences of the actors. Ndorunkundiye, who is 17, had run away from home but later reunited with his family, while Rutagengwa, 19, who believed his parents were killed in the genocide, recently discovered that his father is alive. For both, “Munyurangabo” is their first experience on-screen. They joined Chung for the film’s screening at the Cannes Film Festival, “where they were treated like movie stars,” according to the director.