Washington (CNN) The former commanding officer of the USS John S McCain pleaded guilty to a charge of negligent dereliction of duty resulting in death under the Uniform Code of Military Justice during a court-martial proceeding Friday.

Navy Cmdr. Alfredo Sanchez was in charge of the USS McCain when 10 sailors were killed after the destroyer collided with a merchant vessel near Singapore in August 2017.

Sanchez was arraigned and entered his plea at the Washington Navy Yard. He was sentenced to a punitive letter of reprimand and a forfeiture of three months' pay. In a pretrial agreement Sanchez also agreed to submit a request to retire from the Navy.

In a separate June 2017 incident, seven sailors died aboard the guided-missile destroyer USS Fitzgerald when it collided with a cargo ship off the east coast of Japan. A subsequent investigation by the Navy found both incidents were avoidable and found numerous failures by the crews and commanders of both ships.

The accidents prompted the dismissal of the Navy's 7th Fleet commander, Vice Adm. Joseph Aucoin, as well as multiple reviews of the way the Navy trains, maintains and deploys its fleet.

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