Russian cannibal soldier ate his own comrade, leaked audio from Ukraine's HUR claims
(kyivindependent.com)
There does seem to be an at least western-media-reportable level of known-prior-cannibalism amongst the current forces: https://www.bbc.com/audio/play/p0gvsjgz [it's audio only, sorry - first reputable source I could find]
Whether they knew for the specific person in the current report or not, no idea