Ukrainian filmmaker Mstyslav Chernov was part of the last reporting team in Mariupol before it was overrun by Russian forces. He tells host Marco Werman how he captured life in the besieged city with close-up, personal footage that shows, day by day, the increasingly lethal missile and mortar attacks as most of the city’s residents fled for safety. His film “20 Days in Mariupol” was just nominated for an Oscar for best documentary.