I don't think I can go any more official than the OHCHR, and I don't think I can convince you of your good vs evil narrative with any source. People got shelled, it's obviously implied they got shelled by the other side, and no theory to the contrary is put forward in the report.

I'll let you ponder this: This would be the first conflict in which one side commits all the war crimes. Even more curious, the side which commits no war crimes has a bunch of volunteer units literally using Nazi, SS and Bandera iconography. You know, the guys that marched hundreds of thousands of civilians into the woods and murdered them. Does that seem plausible to you?