The guard would be morally culpable in this life according to the laws of the victors.  His actions would be judged objectively evil.  Based on my reading of the OT, where it reads that God occasionally approves of genocide, don't know what God might make of the guard's behavior.  The bible to me seems a tad bit self justifying when it comes to humanity's penchant for destroying 'others'.  The morality of such acts is usually determined by the victors.  God is beyond my comprehension.  I will let God be God and hope and pray His reality is way beyond the petty self justifying vision of mere men.  In reality the Nazi guard is not so far removed from the torturers of the Inquisition--and they were judged to be doing God's work in a great victory for the Church.  I happen to think that according to current Church teaching the Inquisition was doing Satan's work, but in the end, my opinion doesn't count.