I have a history of violence. We now have something in common, you and I. Society tries to portray monsters as being something other than human, as though we are not all capable of doing horrific things. The UC Stanford prison experiments says otherwise; your own experience says otherwise. I had a year of weekly counseling, in 90 minute sessions, and it was enough for me to understand how to not be pushed toward violence, and how not to depersonalize myself or others to commit violence.
The pressures and duties of your job have warped you to the point where you can no longer be considered an ethical human being. I suggest that you demand UC Davis pay for the years of therapy you will need to process having taken part in a human rights atrocity at their insistence. Your face in the pictures and videos is carefully blank, as though you had to suppress your own personhood and emotional involvement in order to repeatedly use pepper spray at point blank range. If your face had showed you enjoying it, this would be a very different letter. But unleashing that sort of violence feels very freeing, and can become addictive. Unless becoming a situational psychopath is a risk you are willing to take with your own mental health and the physical safety of those around you, please seek treatment.
Good luck, sir.