Last show of the series.
At the beginning, Johnny tells the singer to get the police lieutenant, who was sitting at the bar. This would have taken no longer than 30 seconds, yet the police lieutenant (and the detective with her) did not come outside until much later.
Next, given what had taken place- the gun thug pulling on Johnny, which could be proved via the gun on the ground, making an arrest was very premature. Instead, a competent police investigator would conduct an investigation, to include collecting evidence and witness statements.