I advise public to google the term "staged encounter," "encounter specialist" and the guy called Rao Anwar
If you want more information on the legal use of deadly force in the United States, there is a great book called "Deadly Force - Understanding Your Right To Self Defense" by Massad Ayoob talking about this sort of thing. A lot of the case studies are about police officers.
Edit: This is a good article on the subject too https://www.theatlantic.com/ideas/archive/2018/09/amber-guyg...