FRONTLINE’s 20 Days in Mariupol” is more than a documentary of violence and tragedy in the early days of the Ukraine war against Russia, it's “journalism in action.”

The film follows Associated Press video journalist Mstyslav Chernov and two colleagues as they documented the first 20 days of Russia’s siege, including the bombing of a maternity hospital. By the end of the film, they were the only international journalists left in the Ukrainian city of Mariupol.

“What they captured is really the only document, is the only proof of what happened there,” FRONTLINE executive producer Raney Aronson-Rath told Boston Public Radio on Wednesday.

“What they saw there is heartbreaking. It's important that it was filmed,” she added. “And that's what the film is really made of, are scenes that they were able to capture as they were under siege themselves.”

She hopes the documentary demonstrates the importance of having on-the-ground reporters as eyewitnesses of the war.

“It's really important that we were able to document this for the future, and also for the present, accountability to the governments that are involved in this,” she said.

The film is nominated for best documentary at this year's Academy Awards. Aronson-Rath hopes the nomination will make the film reach more audiences, informing them about the gravity of the situation in Mariupol and across Ukraine.

“This is one story of many,” she said.

“20 Days in Mariupol” is one of four nominees in the best documentary category. The awards ceremony broadcasts on Sunday, March 10.