My Dean threw me under the bus, and I don’t know how to deal with it

I’ll start with the context, I teach a Higher Certificate Course, we have a policy in the end of the year where students who failed but have a threshold above 45% are allowed to resubmit projects or do supplementary exams. I was given a list of students who qualify for resubmission, so that I could let them know what they qualify for. So I create a generic announcement, and send the students the notification, announcing that the subjects they failed, a deadline and a request to make a contact session.

One of the students sees the mail, and emails admin, claiming that it was unfair and that I was an irresponsible teacher, claiming that I had done everything from neglecting feedback (which I incorporate into class, in addition to having to having 6 hours a week reserved for students to organise feedback sessions) to claiming that I had unfairly failed him for two terms despite him having passed those terms.

The admin forwarded this to the Dean, who instead of contacting me, sent a email to the student, with their parents and the admin staff CCd. In the email he just went with the claims and publically shamed me. I feel extremely betrayed and don’t know what to do. I sent a message to him and HR to see if we could resolve this, but I was ghosted.

Does anybody know how I should sort this out, I suck at confrontation, and I’ve been in am depressive state because I feel betrayed.