Third arrest made in murder of North Korean leader's half-brother, while debate over motive continues

Malaysian police have made a third arrest in the apparent murder of Kim Jong-nam, the half-brother of North Korean leader Kim Jong-un and an occasional critic of his family's regime.

On Monday, the leader's estranged brother was attempting to board a flight from Kuala Lumpur to the Chinese territory of Macau when he said he was sprayed with a chemical thought to be a poison, and died shortly thereafter.

Police said the third suspect is a Malaysian man whom they believe is the boyfriend of an Indonesian woman arrested earlier in the day, according to the Associated Press. The other suspect is a woman holding Vietnamese travel documents, who was caught at the airport as she tried to leave Malaysia on Wednesday.

The motives in the attack, however, are not yet known. One source in Beijing, with ties to the North Korea and Chinese governments, told Reuters that North Korea had no involvement in or motive for his death.

"Kim Jong-nam has nothing to do with [North] Korea," the anonymous source said. "There is no reason for [North] Korea to kill him."

US and South Korean intelligence officials disagree. Both specific circumstances surrounding the death – North Korean officials had tried to stop Malaysian police from conducting an autopsy, for example – and a long record of similar assassinations suggest that the hermit kingdom could be involved.

“The North Korean regime has never balked at eliminating dissent and making sure that alternate power centers do not form at home,” Christopher Green, a North Korea watcher and a PhD candidate at Leiden University in The Netherlands, told The Christian Science Monitor on Wednesday. “One aspect of this continuous process is that so-called ‘side branches’ of the Kim family are sent into exile or killed, occasionally one followed by the other.”

As a consensus grows that the country’s political leaders ordered Mr. Kim’s death, multiple theories are emerging for why they singled him out, and why now.

One theory holds that Kim Jong-nam’s ties to China posed a liability to the regime. After an embarrassing 2001 incident cost him the leadership’s favor – he was caught trying to visit Tokyo Disneyland on a forged Dominican Republic passport – Kim Jong-nam later lived quietly with his family in Macau, a semi-autonomous Chinese territory.

In the years that followed, some observers came to believe that China could be protecting him as a possible leader in the event that North Korea’s existing regime collapsed. Beijing considers the North’s stability crucial to its regional interests.

But by sheltering Kim Jong-nam as a step-in leader, the Chinese made him a "constant regime leadership replacement threat" to Kim Jong-un, Robert Kelly, a politics professor at Pusan National University in South Korea, told the Monitor. That threat may have motivated his assassination.

But a different theory holds that Kim Jong-nam’s ties to South Korea, not China, are what made him so dangerous to the regime. Last week, a South Korean newspaper, The Kyunghyang Shinmun, reported that, during the 2000s, he had carried messages between President Park Geun-hye, who is currently suspended amid impeachment proceedings, and then-leader Kim Jong-il – revelations that could threaten the North's official line that its leaders are the only legitimate ones on the Korean peninsula.

Even more damaging, Kyunghyang Shinmun’s report quoted anonymous sources to report that Kim Jong-nam had attempted to defect to South Korea, the US, and Europe – news that could seriously weaken the Kim dynasty’s stature in the eyes of North Korea’s elites and commoners.

The disclosure of this news may have spurred Kim Jong-un to act. But regardless of whether Kim Jong-nam’s ties to China or South Korea – or a separate factor – brought about his downfall, his killing continues a bloody streak.

Since being named supreme leader in December 2011, Kim Jong-un has executed more than 140 North Korean officials as possible threats to his rule, according to the Institute for National Security Strategy, a think tank affiliated with South Korea’s intelligence agency.

"I think [Kim Jong-nam's death] is Kim Jong-un telling the world that there is no chance of regime change," Uk Yang, an advisor to South Korea's Defense Ministry, told the Monitor on Wednesday. 

This report includes material from Reuters and the Associated Press.