Many times we hear of threats involving violence against different factions or groups and some rantings are fruitless with their desires of violence. However, some are very real. There should be an authoritarian with proper knowledge to determine if these threats have any validity and proceed in any actions necessary to limit the loss of life and property against whatever is causing this upset.
North Korea has a history of making threats against South Korea and the U.S. but has yet to do anything but make those threats and continue their attempts at building weapons that would make it possible to carry out the attacks they keep promising. While a watchful eye is needed, it is not necessary at this point to counter the threats with military action, actions that would be far more costly than beneficial.
North Korea, and especially its current leader, have a history of making threats to make themselves seem important. Every country has military drills, and North Korea is no different in this regard. Let them have their drills, there should be no military action until a threat is more immediately imminent.
South Korea and the United States should hold off on military action against North Korea, despite its recent provocation. While North Korea has threatened to turn the countries into "a heap of ashes," no one takes this threat seriously. There should be a consequence, however. This could include further isolation, including from key ally China.