Kudos for being there and supporting. While it can be difficult to give up the adrenaline dumps, and identity it's just simply not worth it any longer. Identity is key, many of us strongly identified ourselves as the job, in fact many still do. Even years after we leave those jobs, we still identify ourselves as "ex-military", "ex-police", "ex-paramedic", "ex-firefighter", etc.

It wouldn't seem natural in such strong and strong-willed people, but what we often need (speaking from experience) is a stronger sense of self and self-worth to take into the next job and being able to separate our "self" and who we are from the job we do.

The political climate and general populace support have turned the job of policing into a thankless, risky role. As you state, his job, family, career all on the line from an event that he had no control over, and in fact even has video that he did nothing wrong. Why should he put up with this? In my eyes it is very similar to the Vietnam war time, when protesters were spitting on and demeaning the same vets that had been risking their lives for them and their government.

I left "the job" after 10 years, and some similar drama/trauma events. So glad I did, likely saved my career and life. I would recommend to your friend to start at least planning for another role, and then either directly transition, or be prepared should an undesired transition take place. Private security gigs, CyberSecurity (pays way better if technically inclined), physical trainer, massage therapist, or many other avenues to suit his skillset are available if he starts directing his efforts.

His mental health will benefit as will his overall health and his families.
2 cents advice from a small fortune in therapy :)
K