The U.S. Atlantic Fleet ordered all non-NCOs (sailors under the rank of E-5, in the E-1 to E-9 rank structure), on its surface ships, to cease standing guard with loaded weapons. This is a temporary measure, until weapons training can be reviewed, and changes made to lower the incidence of weapons going off accidentally. This will require some retraining of the junior sailors, and reminding their NCOs and officers, that more attention has to be paid to the safe use of weapons.
The main cause of all this was four accidental firings of weapons in the last three months by Atlantic Fleet sailors. The Atlantic Fleet has about eighty destroyers, amphibious ships, frigates, cruisers and patrol boats (plus 3-4 aircraft carriers). That's over 20,000 sailors on the non-carrier ships. In the last decade, these ships have had their security greatly increased. First, because of the suicide bomb attack on the destroyer USS Cole, while in Yemen in late 2000. Then came September 11, 2001. Suddenly more sailors found themselves standing guard (or "watch" in sailorspeak) while in port armed with machine-guns and assault rifles. Before 2000, the most common weapon for this duty was a 9mm pistol.
While sailors get some rudimentary weapons training in during their basic training, there is normally little refresher training after that. All this changed after the USS Cole got hit. Ships were given more rifles and machine-guns, and sailors spent more time firing them (usually while at sea). There was apparently not enough training on how easy it is to let off a round from a machine-gun. Three of the four incidents involved sailors in port with M240B machine-guns. This is a 7.62mm weapon that replaced the older M-60 machine-gun. Soldiers, who use these weapons a lot, know how easy it is to fire off a round unintentionally while loading or handling it. The other incident involved a 9mm pistol, which a sailor had put in his holster with the safety off. When he took the pistol out of the holster, he put his finger on the trigger (a big no-no unless you plan to fire the weapon) and it went off, injuring him.
So Atlantic Fleet sailors are going to get an update on how to handle pistols, rifles and machine-guns, especially when the objective is not to fire them. The NCOs (especially the chiefs, as in chief petty officer) were also getting a wakeup call in the form of filling in to stand watch where lower ranking sailors would normally be, at least until the refresher training program was complete. It was the NCOs who were responsible for training the younger sailors in the correct use of firearms, and seeing to it that the lessons stuck.