A South Korean Marine Corps corporal went on shooting rampage on Monday, killing three fellow marines and wounding two others on a Yellow Sea island base near the country's tense border with North Korea, officials said.
The marine was taken into custody, but his motive remained unclear, defense ministry officials said. The officials, who declined to give their names citing office policy, said the corporal, surnamed Kim, was wounded, but it was unclear whether he tried to kill himself or was hurt when he was apprehended.
One of the slain marines was an officer, while the other two were rank-and-file marines, the officials said.
The shooting on Ganghwa Island, about 40 miles (70 kilometers) west of Seoul, was being investigated, the officials said.
The weapon in the shooting could not be identified immediately, officials said, adding that no explosives such as grenades were involved.
South Korea stations hundreds of marines on front-line islands within easy striking distance of North Korea. Last year, North Korea shelled a South Korean island, killing two civilians and two marines.
The waters are claimed by both countries. Boats routinely jostle for position during crab-catching season, and three deadly naval clashes since 1999 have taken a few dozen lives.
In 2005, a South Korean soldier tossed a hand grenade and opened fire at a front-line army unit in a shooting rampage that left eight colleagues dead and several others injured. Pfc. Kim Dong-min later told investigators he went on the killing spree after being enraged by superiors who verbally assaulted him.
The shooting raised questions about the level of discipline in South Korea's 650,000-member military. All able-bodied South Korean men must serve about two years in the military under a conscription system aimed at deterring aggression from North Korea.