A South Korean soldier died Friday after being found with a gunshot wound to his head at a toilet within a guard post (GP) on the border with North Korea, military officials said.

The 21-year-old private first class, only identified by the surname Kim, was found wounded at around 5 p.m. at the GP facility on the eastern section of the border. He died while being taken to a hospital.

In late August, he was dispatched to the GP as a soldier handling thermal observation devices installed at the border. The incident took place when he was on nighttime watch duty, officials said.

"After hearing the gunfire, I rushed to the toilet and found him lying there with a gunshot wound," a senior military official said. 

Military authorities said they are investigating the incident and the cause of his death.

"Abnormal activity by North Korean soldiers has not been detected from the time of the incident to now," an army official said, adding that the incident did not appear to be related to North Korea.