Ukrainians' fight for survival entering its third year

"I cannot get over the feeling that something terrible is going to happen to this city," said Mystislav Chernov, in his documentary, "20 Days in Mariupol."

Something terrible did happen to the Ukrainian city, and Chernov, of the Associated Press, was there to witness it. "What I did not expect is that the bombardment will be so intensive," he told CBS News.

Chernov and his team spent the first 20 days of the Russian invasion inside Mariupol, sending out images that horrified the world, and are now part of an Oscar-nominated documentary. "The whole city was suffering; the whole city was starving; the whole city was without water," Chernov said. "So many people dying."