Dunn graduated cum laude from Boston College Law School in 2013. He had legal internships with the Office of the Prosecutor for the International Criminal Tribunal for the Former Yugoslavia and the Attorney General of Massachusetts, Criminal Bureau. Dunn passed the notoriously difficult New York Bar Exam, and (as of 2015) is an Associate at the New York branch of the international law firm Dechert LLP, focusing on general litigation matters. As of 2021, Dunn is an assistant US attorney at the United States Attorney's Office in Washington, DC.