People always try to come forward.
Rob's death led many people, through his personal information, to analyze that the Lance family was behind it, and that they acted because Rob had betrayed the location of two of their bars to the Dangerous Goods Administration.
Then perhaps the Lance family had bribed someone, obtained the information about the traitor, and ultimately gave Rob a special death by "honorable extermination", leaving him hanging from a streetlamp outside the headquarters of the Dangerous Goods Administration.
Some people, hoping to benefit from the situation, and those from other regions, attempted to report the bars, and they were successful.
So even though things had quieted down in the Imperial District, the arrests in other areas continued.
Director Dale knew it wasn't possible to keep everyone working non-stop. If everyone were kept on edge constantly, their nerves would eventually break.