These friends from Raqqa, Syria, risk their lives to document ISIS horrors in their hometown

— -- A group of middle-class young men from Raqqa, Syria, a city under ISIS stranglehold, is risking their lives to expose the reality of life under the terror group’s reign in their hometown -- horrors that outside media rarely has been able to cover.

These friends-turned-citizen journalists, who call themselves “Raqqa is Being Slaughtered Silently” or RBSS, are now the subject of a new documentary called “City of Ghosts.”

“In my opinion, a camera is more powerful than a weapon,” one of the men featured in the documentary says in Arabic. “And that’s why whoever holds the camera is stronger.”

Oscar-nominated director Matthew Heineman followed their work against the ISIS propaganda machine.

“They really just wanted to protect and expose the horrors of their town, because they wanted to fight for their people,” Heineman told “Nightline.” “The fact that these guys are combating that with sort of counter campaign … to expose the truth, is a fascinating story to me.”

"City of Ghosts," an Amazon Studios, A&E IndieFilms, IFC Films release, opens in New York on Friday, and in select theaters on July 14. The film comes at a pivotal time in the battle to defeat ISIS in Syria and Iraq, as ISIS control is crumbling in Mosul.

Just this week, United States-backed fighters advanced into the city of Raqqa, which has been the terrorist group’s de facto capital since 2013. But despite losing ground, ISIS’s propaganda machine to recruit more to their cause is still going strong, and the mission of these citizen journalists has been to use counter programming to fight it.

Aziz Alhamza and Hamoud Al-Mousa grew up in Raqqa and were motivated to start their activist group to provide footage that serves as a contrast to ISIS’s glossy, highly produced recruitment videos.

“So ISIS was reporting that everything is fine, Raqqa is paradise,” Alhamza told “Nightline.” “And for us we started to film the reality, what's really going on there in the city.”

“ISIS also claimed that all civilians are supporting and welcoming ISIS, and they are enjoying public support, which wasn’t true,” Al-Mousa added in Arabic. “It was our mission to show the other face of ISIS in the city.”

They started capturing and posting stark scenes, such as buildings reduced to rubble and children waiting in never-ending food lines, and brutal scenes of torture of civilians by ISIS.

Their Facebook page quickly became one of the only non-ISIS sources for information.

Alhamza and Al-Mousa were recently in New York City during the week their film premiered at the Tribeca Film Festival. Both of them said they never expected to become activists.

“I don't come from a political background family,” Alhamza said. “I had nothing to do with politic[s], media, whatever. I was a biochemistry student.”

But now, they are considered enemies of ISIS.

“There is a threat against me on social media channel that belongs to ISIS,” Alhamza says in the documentary. "But as we say in Raqqa, ‘death is death.’"

The threats to their lives became so intense that Alhamza, Al-Mousa and many others were forced to flee Syria, but they have figured out a way to continue their work from the outside using an internal team of 17 citizen journalists to feed them information, which they then distribute online.

Alhamza said the lives of those journalists are also in grave danger.

“If anyone notice[s] that they're doing something wrong, taking photos or collecting news, they will be executed,” he said. “But when you believe in something, you will not care about what will happen.”

“They’ve suffered immensely for what they’ve done,” Heineman added. “They’ve lost colleagues, they’ve lost family members. They’re still being threatened by ISIS.”

Al-Mousa, in particular, has paid a heavy price. ISIS executed his father and filmed the whole incident. Al-Mousa said he has watched the video several times.

“Every time I feel tired or that I should stop my work and stay away from the uprising and the media because of everything I have lost, I watch the video and watch the look in my father’s eyes,” he said in Arabic. “It feels like if he is sending me a message to continue what I have been doing and to never stop for the sake of those who died.”

Alhamza is now living in Germany. He and others sought refuge there after ISIS killed one of their own. Even life outside of Syria doesn’t promise safety, they have still continued to get death threats from the so-called caliphate, but they are determined to keep going because Alhamza said others have given their lives for their organization.

“We feel ashamed even to think about stopping this war,” he said.

Alhamza and his group are hoping that one day their work will no longer be necessary and they can move back home.

“I'm still optimistic,” he said.