I don't know if you are aware that in Ukraine there's a sizeable population of ethnic Russians who speak Russian and identify themselves rather with Russia and who could feel hostility during the war and after Why wouldn't they choose Russia as a evacuation route in war ?
As a doctor I wouldn't exclude the possibility that his behaviour could be influenced by the growing tumor.
Some pathologically agressive individuals who had had a long history of antisocial and criminal behaviour were later found to be genetically determined by a kind of neurotransmitter mutation(s).