"(He) then exited the vehicle and continued fleeing south" across the military demarcation line after being shot by North Korean troops, according to the United Nations Command.
The individual, presumed to be a North Korean soldier, "initially took cover near a building on the southern side of the JSA," the UNC said, using the abbreviation for the Joint Security Area (JSA).
Four North Korean soldiers chased him, firing shots with their pistols and AK-47 rifles, an official at the South's Joint Chiefs of Staff said, citing CCTV footage of the scene.
He was hit by five rounds while running away from the North in the area inside the heavily fortified demilitarized zone, he added.
It's also unclear whether the North's troops actually crossed the MDL, even for seconds, during the hunt.
He was recovered by South Korean and US soldiers later Monday and transported to a hospital south of Seoul,
He underwent a surgery at Ajou University Hospital in Suwon and is still unconscious.
He's in critical condition, and it's unclear whether he will live, given the seriousness of the wound, according to Lee Cook-jong, a doctor at the hospital.
"(We) will have to ride out the crucial moments (in his recovery) over the next 10 days," he told reporters.
The JCS confirmed that the North Korean man approached the JSA by car at around 3:15 p.m. Monday.
The car sped towards a guard post but its wheels fell into a nearby drain, the JCS spokesman Army Col. Roh Jae-cheon said earlier. At the time of the defection, the soldier was clad in the Korean People's Army uniform and had no weapon, he added.
"We closely monitored the situation with a surveillance system," Roh said.
At a parliamentary defense committee session, Suh Wook, the chief director of operations at the JCS, said that Seoul's military believes four North Korean soldiers fired about 40 shots towards their runaway comrade.
"Three North Korean soldiers, along with one from a guard post, went after him and fired at him," Suh said. "At 3:31 p.m., we detected one defector who fell to the ground among fallen leaves 50 meters from the MDL," he added.
At the same session, Defense Minister Song Young-moo said the incident marked the first time the North had fired shots into the South Korean side of the JSA.
Song simply answered, "Yes," when Liberty Korea Party Rep. Chung Jin-suk asked him if this was indeed the first such case.
JCS officials said later there's a bullet mark on the southern side but an additional probe is needed to confirm whether it's associated with the latest firing incident at the JSA.
As for the South Korean military's response, Song said, "I think our military minimized the damage and handled the defected soldier well in such a short period of time."
When pressed if North Korea had violated the terms of the armistice, Song said he would ask the UNC's Military Armistice Committee to take appropriate measures.
"If our request is not met, then we'll have no choice but to take legal steps and release a statement, among other measures," Song added.
There was no report of any exchange of fire between the two Koreas.
A North Korean soldier defected to the South via the JSA in 1998 and another in 2007.
The UNCMAC is looking into the incident.
The commission notified the North's military that the individual is being medically treated at this time.
The message was conveyed verbally since there's no other communication channel between the two sides and the North's guards at the JSA listened to it, a UNC official said. (Yonhap)