When Lt. Eckstrom explains the layout of the apartment building to the detectives, he points to the apartment where the stakeout will take place, then points to a room just below it and tells the detectives to be sure to avoid contact with the other tenants. The room he points to is a bedroom in the stakeout apartment, so no tenants would be in that room.
The goof item below may give away important plot points.
There is a layer of dust or powder all over the floor of the bank, as can be seen when the guard is shot and goes down. This is, presumably, to prevent reflections from the polished floor as evidenced by a bare spot and the still-visible reflections of white table legs at the top of the frame.