 PLOT: After Inspector Callahan, in civilian clothes, leaves the  coffee shop one of the armed robbers tells the customers they "did  real good in front of that cop," implying that the robbers knew  Callahan was a cop who came in the coffee shop that time every day.  If the robbers knew a cop came in at a certain time, even the  dumbest crooks would have known not to stage an armed robbery until  after the cop left.