How does Wiesel describe Dr Josef Mengele?

From the text:

The wind of revolt died down. We continued to walk until we came to a crossroads. Standing in the middle of it was, though I didn't know it then, Dr. Mengele, the notorious Dr. Mengele. He looked like the typical SS officer: a cruel, though not unintelligent, face, complete with monocle. He was holding a conductor's baton and was surrounded by officers. The baton was moving constantly, sometimes to the right, sometimes to the left.