I think majority of people fighting for Ukraine are shopkeepers, teachers, mechanics, engineers, farmers and so on. Very much just average people, with quick training, defending their own country against violence and pretty literal existential threat while receiving news about bombing of childrens hospital. And there's been stories around where Russians pretend to surrender and set up an ambush on the site.

I can understand why individuals choose to kill anyone with a russian uniform regardless of the situation. War is a terrible thing and it brings out the worst from us. Here in Finland if you ask a veteran on how it feels to kill a human being they'll likely answer that they don't know as they've only killed enemies. I believe many Ukrainians respond similarly.

It obviously doesn't make it right, war crimes should be punished regardless on who made them, but I can understand why normal people do fucked up things in fucked up scenarios and war is pretty much at the top of fucked up scenarios.