As head of the New York City Medical Examiners Office, Hirsch and six aides went to establish a temporary morgue for the victims of the September 11, 2001, attacks at the World Trade Center. When the North Tower collapsed, two members of the team were severely injured and Hirsch was thrown to the ground and bruised over much of his body, and left covered with dust over his entire body. Emptying the pulverized concrete from his pockets that day, Hirsch realized that many of the victims would have suffered a similar fate and been "rendered into dust". The Chief Medical Examiner's office has been responsible for the identification of the 20,000 body parts recovered at the site, and has used DNA and other medical technology to identify the individuals and to notify their families.