One aspect that doesn't appear to have been mentioned yet is the "killology" training that many police officers around the US receive from Dave Grossman.
From a Mother Jones article
Over the past two decades, Grossman has achieved semi-celebrity status as an authority on aggression, close combat, and the psychology of violence. He literally wrote the book on killing, On Killing. His books have been translated into several languages and he says they are required reading at the FBI Academy and many law enforcement academies. He’s lectured at West Point and claims to have conducted trainings for every federal law enforcement agency, every branch of the armed forces, and cops in all 50 states. For more than 19 years, he’s been on the road, leading seminars and trainings nearly 300 days a year.
“Dave Grossman tell him that every single traffic stop could be, might be, the last stop you ever make in your life.”... says Seth Stoughton, a former cop and law professor at the University of South Carolina who studies the regulation of police. In Grossman’s worldview, Stoughton says, “the officer is the hero, the warrior, the noble figure who steps into dark situations where others fear to tread and brings order to a chaotic world, and who does so by imposing their will on the civilians they deal with.”
A Slate article
points out that,
Grossman wants cops to develop “autopilot responses” so that they will not be caught flat-footed when confronted by an armed suspect. “Is it possible to see a gun pointed at you, draw your own weapon, and shoot without conscious thought?” Grossman asks. “Not only is it possible, in this case it is highly desirable. Of course, his training must be state-of-the-art, so that he knows instantly that the threat is indeed a gun, and not a wallet or a cellphone.” In practice, many cops have had trouble clearing this threat-assessment barrier...
“As a cop, or a peacekeeper, your job is not to kill. It is to serve and protect. To do that, you may have to kill,” he says in Unit 4. “The most effective way to stop someone is to fire a bullet into his central nervous system. It is up to God and the paramedics as to whether the man dies. Your job is to stop the deadly threat, and the most effective way to do that is to make the threat die.” Throughout “On Combat,” Grossman is very, very clear that police officers must be ready to manifest the will to kill...
Minneapolis Mayor Jacob Frey banned warrior-style training in Minneapolis in April 2019, calling it "fear-based."... But Grossman's course is still continuing elsewhere.
I don't think it's overstating things to say that Dave Grossman has had a major impact on US policing over the last 20 years and has led forces all around the country to see themselves at perpetual risk from the public they purport to protect and serve. As Seth Stoughton notes
"If officers look at the people that they interact with as enemy combatants, as potential threats instead of community members whom officers are supposed to be serving and protecting, it's really not a surprise when they disregard the value of someone's life"