Student Threatened Me after He Failed the Exam

One student submitted the wrong answers with wrong file format in final test. After I refused to increase his score, he writes this:

“Out of respect for you as well as to keep you in the loop I'd like to notify you that I will be contacting and meeting with the Office of The Dean in regards to the matter. I hope to hear from you soon.”

In fact, after years of professorship, I am not surprised at all.