Police say a retired police lieutenant shot and killed a fellow officer during a training exercise in Washington.

Jesse Porter was at the end of a training exercise at a library in the Anacostia neighborhood when he fired a weapon and hit a woman. The library officer was taken to the hospital where he died.

Police consulted with the U.S. attorney's office in Washington before arresting Porter. It wasn't clear if he had an attorney who could make a statement on his behalf.

The retired lieutenant discharged a single shot from his gun while he was training a group of police officers on how to use batons.

Other library police officers were in the room with about six others. The city's public library system has its own force of full-time special police officers who can be armed and are responsible for ensuring the safety and security of the libraries.

It was not clear why Porter had a gun during the training exercise. Trainers and participants in training programs shouldn't have access to live bullets or actual firearms in order to avoid accidental gunfire.

It is not good practice. I don't know why the trainer had a live weapon. It's not a good idea to do this.

Police said the investigation into the shooting was still ongoing.