A British court has sentenced a Royal Navy sailor to 25 years in jail for shooting an officer to death and firing at three other crewmen on a British nuclear submarine.

Able Seaman Ryan Donovan admitted Monday that he killed Lieutenant Commander Ian Molyneux on the HMS Astute, while the submarine was docked in the port city of Southampton in April.

Justice Richard Field of the Winchester Crown Court described the killings as a “murderous onslaught.” Donovan was drunk at the time.

The 23-year-old sailor also admitted to the attempted murders of three other crewmen . Donovan fired an SA80 rifle numerous times before the weapon was wrestled away from him.

The shootings took place as local dignitaries, including Southampton's mayor, were being given a tour of the submarine during a goodwill visit to Southampton.