(throwaway account)
Boss didn't reprimand or fire the coworker who came at me in an aggressive and threatening manner, which the coworker has done to me before (first time was documented and nothing came of it either). Boss didn't accept my immediate resignation and just demoted me to another department to keep me out of swinging-reach of the coworker. I did not feel bold enough to get up and walk out anyway because I didn't want to come off as the aggressor nor burn the bridge in case references are needed for future employment.
I'm struggling with how to compose a professional yet firm email to my boss stating that I am leaving due to not only how the person has abused me (the violent outbursts are the only incidents that have been brought to their attention because my safety was at risk, but I have documentation of many other incidents of verbal and psychological abuse) but also because of how they have twice now dismissed these violent outbursts.