Saturday's deadly shooting incident has prompted calls for the military to enhance its management of "draftees requiring special observation."
The 22-year-old sergeant, who killed five soldiers and wounded seven in a shooting spree, turned out to have once been rated as a Grade-A soldier ― the class of draftees most in need of special observation.
Although the sergeant, identified only by his surname Lim, was later rated as a Grade-B soldier who still needed extra care but was able to carry out frontline service, critics argue that it was a mistake to allow him to work at a general outpost with a rifle and grenade on a daily basis.
The draftees requiring special observation are divided in three grades, with Grade-A being the most severe.
They include those who could become violent, or previously attempted or could attempt suicide. Also among them are those who are parentless or from poor families; mentally or physically weak; or homosexual.
The combined number of closely observed draftees in the Army, Navy and Air Force is approximately 7,000. In the 22nd Division, in which the shooting occurred, there are some 1,800 soldiers under special observation, some 20 per cent of the troops of the unit in charge of controlling the eastern border.
Under the military rules, those soldiers are to receive extra supervision from unit leaders.
Due mainly to a shortage of troops for border control, the frontline units cannot just let the potentially dangerous draftees take secondary missions, officials said.
"If we exempt all the draftees under special observation from the vigilance duty, it is very difficult to maintain our mission," an officer told media, declining to be named.
The system to better supervise risky soldiers was instituted in 2005, after a soldier went on a shooting spree, killing eight troops.
Since then, the military has conducted regular personality tests to identify those who are unfit for frontline missions.
Military authorities have provided mental treatment and counseling to those who suffer from depression and could attempt suicide.
They also send soldiers who are highly suicidal to rehabilitation centers, called the Green Camp or Vision Camp.
The military has also dispatched professional counselors to regiment-level units. It initially planned to send a total of 350 counselors to those units by 2017, but only 200 or so are currently on site due to budgetary constraints.
Observers say that more counseling staff should be deployed to lower-level units, particularly to frontline outposts given the level of mental distress suffered by border guards.
Cut off from the rest of the world, Army soldiers in charge of border control usually spend a maximum of one year standing watch in a small, remote observation spot for many hours each day.