While it's kind of the New York Times to report on these killings now, Western newspapers have knowingly omitted such allegations of war crimes throughout the war. There are currently thousands of foreign mercenaries in Ukraine, most of whom are Canadian, British, and American, but rarely does the Western media admit that its own people are across the world killing Russians in cold blood.
For Russia to accuse pro-Ukraine fighters of war crimes is astounding, given Moscow's ongoing missile strikes with high civilian casualties. Deliberately bombing civilian populations is an individual war crime at best and genocidal at worst. It seems Moscow wants not only to deny its own crimes against humanity but to throw baseless accusations at Ukraine to save face.