Given the tragic shooting at the ROK Marine post on Kanghwa Islandit was probably unfortunate that the ROK Army announced on the same day plans to open an Army shooting range to the public. Given the recent events I suspect that this statement will change (my emphasis given):
The official said that they have not drawn up specific safety measures as a private organization that will primarily run the ranges has yet to be selected. But the plan is to conclude a memorandum of understanding (MOU) with the chosen entity within the month. (Source)
This is the worse incident since the 2005 shooting tragedy at an Army post when 11 sleeping soldiers were killed by one of their own on a shooting and grenade rampage. The Army tightened up weapon and ammunition access after that incident so maybe in this latest incident the marine was able to circumvent those controls or there has been a relaxation of regulations due to the tensions between the Koreas.
As terrible as these incidents are, the worse case would be for inter-Korean tensions to increase further and another one of these shootings to occur but somehow be mistaken during the incident by the local troops as a North Korean attack. Most shots across the DMZ are responded to in a controlled manner but given the shelling of the West Sea island last year, a local commander could mistake gunfire and more so grenades for an attack. I think this possibility is low but it is an extra dimension to consider as Korea enters into what the well respected North Korean expert Andrei Lankow described as the most dangerous time in Korean history of the past 25 years. Given the amount of weapons available these incidents appear rare, although I am not sure how they compare to other countries with militaries who have such regular access to live ammunition and weapons. The military will probably be very observant over the next few weeks to prevent copy cat incidents, especially due to the prevalence of social media in South Korea. Hopefully, these incidents will remain very limited occurrences.