SEOUL (Reuters) - A South Korean marine went on a shooting spree on Monday at a base near the tense maritime border with North Korea, killing four fellow soldiers before trying to blow himself up with a hand grenade, the military said. The incident was not related to the ongoing inter-Korean conflict which has simmered since 1953 when the Korean War ended in a truce, not a peace treaty. "After firing his K-2 rifle inside the marines' living quarters, a hand grenade was detonated in a separate building compartment outside," marine's spokesman Colonel Kim Tae-Eun told a press briefing.