why is montag irritated by the situation at this fire?

One evening, an alarm comes in, calling the firemen to an old house where the owner, an older woman, refuses to abandon her home. Defiantly, the woman insists on dying among her books and lights the match that eventually takes her life along with her home and all her books. During the melee, Montag steals one of the woman's books and takes it home with him that evening. Montag returns home shaken by the woman's death and nervous about his illegal acquisition.