With the picture material available I would like to challenge the frame of your question.
The picture seems to show multiple German soldiers in uniform (although only parts probably because parts were taken off for intensive labor) carrying what looks like it might be a dead body while an armed and properly, but differently uniformed soldier is standing in the front.
This would be highly improbable being filmed in a still working death camp. No German soldiers would have done physical labor with hundreds of prisoners around to be used as forced labor. And German soldiers would not need a guard.
What this most likely shows is a scene after the liberation of the camp where German prisoners of war were used to clean up the camps, removing the dead victims and burying them. An allied soldier is standing guard over them. From their uniform and weapon I would assume the guard is British. For example compare the obvious German cap in the left with the very British looking cap of the guard.
That explains why it's a British rifle in the foreground.