Mstyslav Chernov’s “20 Days in Mariupol,” a harrowing first-person account of the early days of Russia’s invasion of Ukraine in 2022, won the best documentary Oscar on Sunday. A joint production of The Associated Press and PBS' “Frontline,” statuettes were awarded to Chernov, producer and editor Michelle Mizner and producer Raney Aronson-Rath. The Oscar — and nomination — was a first for both Chernov, an AP video journalist, and the 178-year-old news organization.