Well, Betty is a really extremely intelligent man. He is Montag's captain, and he presents a paradox. He knows that Montag is constantly hiding his interest in books, and he doesn't do nothing. The first time that Betty and Montag are introduced, it is noticeable the conflict between them. According to the statement "Hell! It’s a fine bit of craftsmanship, a good rifle that can fetch its own target and guarantees the bull’s-eye every time...Why? You got a guilty conscience about something?" is an example of Betty's perceptiveness about Montag and throughout the book, he likes to toys with Montag and manipulates him.
This seems to be a declarative sentence. It talks about the reaction of the policeman to a specific thing. His expression is not pleasant. What he might saw is something not good and something to worry about. Other possible thing could be there an heinous crime scene that he faced at that moment. It depends on the situation.<span />
