After directing the Oscar-nominated documentary Cartel Land, on the vicious drug war spanning the U.S. and Mexico, Matthew Heineman would have been forgiven for taking on a less dangerous assignment for his next film. Instead, he turned his attention to an even deadlier conflict, Syria’s brutal civil war, for his harrowing City of Ghosts.

The film, which recently made the Oscar documentary shortlist, centers on members of Raqqa Is Being Slaughtered Silently (RBSS), a heroic group of citizen journalists who risked death to report on atrocities committed by ISIS in their hometown.

“The film basically follows them after members of the group were killed and [survivors] were forced to flee,” Heineman tells Deadline. “I was with them as they were fleeing from Syria to Turkey and then ultimately to Europe as they continued to be hunted by ISIS, moving from safe house to safe house.”

The citizen journalists incurred the wrath of the terrorist organization by daring to counter the myth propagated by ISIS that it had turned Raqqa—the capital of its self-styled caliphate—into a paradise on earth. Members of RBSS secretly recorded video demonstrating Raqqa under ISIS had in fact become a hellscape of harsh conditions and hideous public executions.

“When ISIS took over my city the main thing they focused on was how to spread their propaganda to recruit people all over the country, all over the world. They were able in a short time to recruit thousands of people from 84 countries,” explains Aziz Alhamza, RBSS founder and chief subject of City of Ghosts. “It was a duty to do something to show the reality, otherwise ISIS will be able to recruit more people.”

Amazon Studios

Heineman made the decision to show deeply disturbing images taken by RBSS members, including the crucifixion of a man in a public square.

“For me I didn’t want to shy away from the violence. I think that would have been an injustice to the true horror and fear that the citizens of Raqqa have lived with every single day,” Heineman declares. “It was very much a balancing act of showing the violence, but also being cognizant of how intense it was…The story is about image-making, the power of images. We’re not trying to use violence in a pornographic way. It’s inherently part of the narrative this film is telling.”

Since the film’s theatrical debut last summer ISIS has been driven out of Raqqa and its footprint sharply curtailed in other parts of the Middle East where it previously reigned. But Heineman believes it would be a grave mistake to consider ISIS eradicated.

Amazon Studios

“The sad reality is that to members of Raqqa Is Being Slaughtered Silently and to many people, ISIS is an idea, and you can’t beat an idea. You can’t win a battle against an idea with bombs, with guns, or militarily,” Heineman observes. “What remains is this ideological battle. And I think the question we pose in the film is, how do we as a global community, how do we as citizens, as governments, as journalists, fight ISIS as an idea, fight this extremist ideology that not only took over Raqqa but has been exported from Raqqa to other places all across the world? And I think that is a question that we don’t have an answer for—‘we’ being the U.S. government and other governments.”

City of Ghosts is currently available on Amazon and iTunes. For Heineman, making it presented a particular set of challenges.

“This is definitely the hardest film I’ve made thus far, by far. Just the nature of following a group of people who are fleeing for their lives, moving from safe house to safe house [and] by nature don’t want to be seen…Making sure we were diligent in how we were communicating and making sure we weren’t exposing anybody more so than we necessarily had to—these were all extremely difficult things to navigate,” Heineman explains. “And then cinematically it was also quite difficult because it’s sort of the opposite of my last film, Cartel Land, which was a visual feast out of this Wild West of Mexico and really anywhere you pointed your camera was interesting. This film, the drama partly took place in these safe houses, in these closed smoky rooms…[with] a group of guys sitting around. Trying to find the humanity in that, the drama in that, the cinema in that was a big challenge.”

Amazon Studios

Heineman heads into 2018 with a full slate of projects. His documentary series The Trade, which explores the opioid epidemic from both sides of the U.S.-Mexico border, holds its world premiere in January at Sundance. And he will be continuing work on A Private War, his first fictional film that stars Rosamund Pike as the late war correspondent Marie Colvin.

On January 23 he will learn whether City of Ghosts earns an Oscar nomination for Best Documentary Feature.

“I’m extraordinarily honored to be on the shortlist,” he tells Deadline. “There’s so many incredible films out there, so many incredible films about Syria this year. I’m even more moved that this means so much to the members of Raqqa Is Being Slaughtered Silently, that hopefully this will give greater recognition, greater exposure to the incredibly important work that they do.”

He adds, “This film is many things to me, but partly it’s an homage to journalism, an homage to people fighting for the truth, especially in an age where truth, the facts, seem to be malleable.”