“I’ll never forget that day in Auschwitz, the first time in Mauthausen. At that second place, as time wore on, I also picked them up from the bottom of the great cliff, when their escapes fell awfully awry. There were broken bodies and dead, sweet hearts. Still, it was better than the gas. Some of them I caught when they were only half-way down. I shiver when I remember-as I try to de-realize it. I blown warm air into my hands, to heat them up. But it’s hard to keep them warm when the souls still shiver. God. I always say that name when I think of it. God. Twice, I speak it.
Please believe me when I tell you that I picked up each.”
In this quote, what is the symbolism for "shivering souls"?