I read the article as strongly implying that individual Americans are complicit in war crimes in Ukraine, at least to the extent of not reporting them. It's possible the article is wrong or misleading, or that the source mislead the journalist, but after the clear descriptions of Americans killing Russians on the battlefield I read "I don’t know what happened to them" to be a intentional strong wink that the captured Russians were not treated in accordance with the Geneva conventions. Do you interpret it literally?