WASHINGTON (DC News Now) — The Metropolitan Police Department (MPD) said a library police officer died Thursday afternoon after a retired police lieutenant shot and killed her in the Anacostia Library.

MPD said the retired lieutenant was conducting training at the library, located at 1800 Good Hope Rd. SE. At the end of the training, the retired lieutenant fired a gun. The bullet hit the library police officer.

Medics took her to the hospital where she died.

Other library police officers, as well as the retired lieutenant, were being interviewed late Thursday afternoon.

MPD said it was working with its partners at the U.S. Attorney’s Office for the District of Columbia in the investigation into exactly what happened.