The nation’s first African American Librarian of Congress was the latest person to get fired by President Donald Trump, a move that librarians say could stymie progress in making the nation’s library more accessible and inclusive.

The Library of Congress, a 225-year-old Washington institution, has never had a moment like this. Last week, the Trump administration fired the longtime librarian of Congress, Carla Hayden.

The dismissal of Librarian of Congress Carla Hayden has triggered a group of Democratic lawmakers to request an investigation of potential improper communication.