A Ukrainian medic smuggled footage of Mariupol's horrors to AP reporters before they left the city.
Yuliia Paievska's footage showed her tending to wounded Ukrainians - and even Russians.
A day after she snuck out the video, Russian forces abducted her. Her whereabouts are unknown.
A Ukrainian medic was captured by Russian forces in mid-March after sneaking out video evidence of the war's devastation.
Yuliia Paievska - known in Ukraine as Taira - recorded 256 gigabytes of harrowing and graphic footage from a helmet camera in Mariupol over a two-week period during Russia's siege on the city, the Associated Press reported on Thursday.
Taira, 53, handed off the camera card to an AP team. The team of journalists - one of whom hid the evidence in a tampon - made their way through over a dozen Russian checkpoints before they escaped the strategic southern port city in a humanitarian convoy, the report said.
Taira was captured by Russian troops the next day, the report continued. Russian broadcasters aired a video of her and accused her of trying to flee the city in disguise. She hasn't been seen since.
The footage, published in Thursday's report, documents the efforts of Taira's team to save the lives of wounded Ukrainians - and even Russians.
In one video, a team of medics could be seen trying to save a young boy's life. He didn't survive, and Taira turned away - placing a bloodied hand on a wall. The helmet footage picked up sounds of her sobbing, as medical devices beeped in the background. She then shut the boy's eyes.
Another video published by the AP showed Taira removing bloodied gloves from her hands, before moving to footage of her hustling down a hallway behind first responders as they pushed a stretcher.
The following frame showed Taira tending to the wounded and bloodied face of a man - opening his eyelid with extreme caution as he took deep breaths.
More footage from Taira's helmet camera showed a soldier being carried away on a stretcher, before cutting to a shot of a soldier's bloodied face getting bandaged by medics. In the next frame, medics performed CPR on an unidentified person.
Since her abduction, a website was published showing how long Taira has been in Russian captivity since March 16 - 65 days and counting. Efforts between Ukraine and Russia to involve her in a prisoner swap have stalled.
Her husband, Vadim Puzanov, told the AP that he had little to no knowledge of her whereabouts or condition. The website said Russian state media had tried to use Taira in disinformation and propaganda campaigns.
"Accusing a volunteer medic of all mortal sins, including organ trafficking, is already outrageous propaganda - I don't even know who it's for," Puzanov said.
Medics, hospitals, and other healthcare facilities have consistently been targeted by Russian forces throughout the three-month war.
Editor's Note: A previous version of this story incorrectly stated how the camera footage was smuggled out of Mariupol, Ukraine. The camera card was handed off by the medic to a team of AP journalists, one of whom hid it in a tampon.