This is a backdoor pilot that introduces the cast of Chicago Justice (2017), a spin-off of Chicago PD (2014).
Lorraine Toussaint reprises her role as defense attorney Shambala Green from Law & Order (1990). Green last appeared in Identity (2003) 13 years earlier.
This episode was inspired by the Philadelphia Police Shooting in which an individual rushed towards and shot Philadelphia police officer Jesse Hartnett while he drove his patrol car, inserting the gun into the window of the car and firing at point blank range. Despite being shot multiple times in the left arm, Hartnett was able to exit his car and shoot the fleeing suspect.