This is utterly tragic. Not sure that there’s a lesson to be learned other than life is short and people can be unpredictable. Must be so hard for his sister and family.
My takeaway is if I discover a crime being committed by someone I don't know well, report and cut all contact. Upgrade Security. Be alert. This whole situation is a tragedy, and his willingness to impart reason with the unreasonable cost him his life.
