The entire article is worth reading, but here the most relevant part for your question:
"One teaching method he cited, however, was a chart of different mental states – each assigned its own color – describing levels of preparedness, or the lack of it, to respond to threatening situations. The chart was developed by former U.S. Marine Col. Jeff Cooper, now deceased, “as a means of setting one’s mind into the proper condition when exercising lethal violence,” according to a 2004 written commentary attributed to Cooper.
Kennedy features a fighting practice in an instructional video, showing him and students wrestling and trying to tackle one another. He described the practice as a form of “stress inoculation” that aims to improve officers’ performance under pressure."
The entire article is worth reading, but here the most relevant part for your question:
"One teaching method he cited, however, was a chart of different mental states – each assigned its own color – describing levels of preparedness, or the lack of it, to respond to threatening situations. The chart was developed by former U.S. Marine Col. Jeff Cooper, now deceased, “as a means of setting one’s mind into the proper condition when exercising lethal violence,” according to a 2004 written commentary attributed to Cooper.
Kennedy features a fighting practice in an instructional video, showing him and students wrestling and trying to tackle one another. He described the practice as a form of “stress inoculation” that aims to improve officers’ performance under pressure."
https://www.reuters.com/investigates/special-report/usa-police-extremism