Was he from Poland?
Yes, the Russians are brutal and ruthless. The Nazi–Soviet Pact is a big factor that allowed the war to start, because Hitler knew how dangerous the Russians can be (the country is hard to invade and Russian leaders never cared about their human losses). He thought he would buy time before invading them. In the end, Operation Barbarossa was too precipitated anyway (Hitler's generals were better than him, he should've listened to them).
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Anyway, your grandpa's instincts was to protect his sisters and mother (even if apparently he couldn't). I won't discuss if it's natured or nurtured, but, in any case, society knew that risking one's life to protect others has great value.