It's Getting Dark(2016)

"Hello Rufus! Today they took my mother..." A little Dwarf writes to his brother from Magnitogorsk to Moscow. Karik is only 10 years old, but he already knows words like “search" well. Only when he goes from the description of the arrest to the description of the birthday dinner, you can guess what the child is writing. This letter will soon be eighty years old, but it could have been written today. After all, each of the numerous child heroes of this film has already experienced the same thing as Karik in Stalin's time.