South Korea\'s military said Sunday it will punish two commanders for failing to prevent a shooting rampage by a marine soldier last week that left four troops dead. A 19-year-old corporal last Monday went on a shooting spree at an elite Marine Corps. unit near the tense sea border with North Korea, killing four soldiers and wounding another. The corporal, only identified as Kim, was also injured after detonating a grenade in an apparent suicide attempt. His condition is not life-threatening. A colonel and a lieutenant colonel from the unit at Ganwha island west of Seoul will be removed this week from their positions as commanders, the Marine Corps. said in a statement. \"The two will be waiting for further actions by the disciplinary committee,\" a Marine Corps. spokesman told AFP, adding there was no plan to discharge them. The military last week arrested a private for allegedly helping Kim steal ammunition from a weapons storage room before the corporal opened fire at a barracks. Kim and the private, surnamed Jung, told military investigators they had hatched a plan after being constantly bullied and beaten by superiors, but Jung denied involvement in actual shooting. Military psychological tests conducted about a year ago found Kim was mentally unstable and struggling to cope with service life, investigators have said. He had also been drinking before the shooting. The elite Marine Corps is charged with guarding frontline islands in the Yellow Sea near the disputed border with the North. But last week\'s incident -- the third to afflict the military in six years -- raised questions about standards of discipline in the South\'s largely conscript 650,000-strong military. Able-bodied South Korean men must undergo at least two years\' military service. But some complain of abuse and harassment within the armed forces. South Korea\'s defence minister Kim Kwan-Jin on Saturday sent an emergency order for all military commanders to investigate and report unfair practices at barracks by September, Yonhap news agency said. Eight soldiers were killed and two seriously injured in 2005 when a soldier threw a grenade and sprayed bullets over sleeping colleagues at a frontline guard post north of Seoul. The attacker alleged senior colleagues had bullied him. In 2008 an army private struggling to adapt to military life threw a grenade at colleagues who were asleep, injuring five.