What is Wolff's purpose for describing the eyes of the man with the pistol?

As Anders feels only the tiniest beginnings of worry at this point in the story, the reader is already very concerned about the safety of everyone in the bank. Wolff increases this feeling of anxiety by describing the man with the pistol's eyes. Saying they are red and raw and that one of his eyelids twitches incessantly points to the man's impulsivity, lack of rest, and likely state of desperation. All of these elements raise the stakes of the situation significantly.