He reportedly told medical workers he had been attacked with a chemical spray, and South Korea's intelligence agency believes he was poisoned. And if they did, they'd likely need some plot explainers - few know Kim Jong Un even had a half-brother.
"Investigation is in progress and a post-mortem examination request has been made to ascertain the cause of death", the statement said.
Multiple South Korean media reports said he was killed at the airport by two women believed to be North Korean agents. While there's no evidence yet linking the murder to Kim Jong Un, South Korean lawmakers and observers of the secretive regime see him as the clear victor.
Repeated calls to South Korea's spy agency seeking comment went unanswered.
Earlier on Wednesday South Korea's spy agency said two women believed to be North Korean operatives poisoned the 45-year-old exile in a shopping concourse at Kuala Lumpur worldwide airport.
The Royal Malaysia Police issued a statement saying they had arrested a woman claiming to be 28 years old and born in the Vietnamese city of Nam Dinh.
District police chief Abdul Aziz Ali said he was waiting for a flight to Macau.
The South's MOU, however, is yet to officially confirm the alleged murder of Kim in Kuala Lumpur.
This took place despite North Korean objections about an autopsy taking place.
As former leader Kim Jong-il's oldest son, Jong-nam has been said to represent an alternative locus of legitimacy - if not power - within North Korea, where rumblings persist that Kim Jong-un's power consolidation project remains incomplete.
Kim Jong Nam, 46, the estranged half-brother, was targeted on Monday at a low-priced carrier terminal at the airport, a senior Malaysian government official said. He is believed to have been born May 10, 1971.
Analysts had long considered Kim Jong Nam, as the eldest son of second-generation leader Kim Jong Il, to be the natural heir to the family dynasty.
Recently, South Korea had tried to negotiate Mr Kim's defection but failed, The Korea Herald reported.
Kim Jong Nam, who was 45 or 46, was estranged from his younger brother, North Korean leader Kim Jong Un, and had been living overseas for years.
News of the murder came two days after Kim Jong Un test-fired a ballistic missile as part of efforts to develop North Korea's nuclear-weapons capability.
North Korea is reported to have asked that Jong-nam's body be handed over to its embassy in Kuala Lumpur.
Their relationship probably took a turn for the worse in 2013, when the young North Korean leader ordered the execution of their uncle, Jang Song Thaek.
The NIS also cited a "genuine" attempt by North Korea to kill Kim Jong Nam in 2012, the lawmakers said.
But the opaqueness in North Korea also opens room for speculation about the motives behind the killing and whether it could be traced back to high-level decisions in Pyongyang. She has not been seen in public for more than three years, Gause said.
"As soon as the truth is revealed, it will have a strong influence on the political situation in North Korea, as well as relations with neighboring states", Ba said. Kim Jong Nam's bore the name Pang Xiong - "fat bear" in Mandarin Chinese.