Police say Kim Jong Un’s half brother was killed with a nerve agent. What are the clues to this bizarre international mystery?

Reporting from Seoul, South Korea —  The apparent assassination of North Korean leader Kim Jong Un’s half brother this month is a bizarre, unfolding story that has sparked media frenzies and diplomatic tensions across Asia.

The saga began two weeks ago with a brazen public attack, caught on closed-circuit television, inside a major international airport in Kuala Lumpur, Malaysia. Police said Friday that VX nerve agent, a chemical classified as a weapon of mass destruction, was found on the face of the dead man, Kim Jong Nam.

Two women, apparently aided by North Korean agents, are the suspected assassins, according to Malaysian police. Some of the suspects are hiding behind diplomatic immunity to avoid investigators.

In another development, someone this week apparently tried to burglarize the hospital mortuary where Kim’s body is awaiting positive identification.

Each day brings new revelations — and new questions. Here’s what we know so far:

Who is Kim Jong Nam?

Kim, 45 or 46, is the half brother of Kim Jong Un, the current North Korean leader and grandson of Kim Il Sung, the patriarch of communist North Korea.

Kim Jong Nam was believed to be the first son of Kim Jong Il — the former North Korean dictator who died in December 2011 — which he had with one of his mistresses, the late North Korean actress Song Hye Rim.

In recent years he lived in the Chinese region of Macau. He has children there and in Beijing. It’s unclear whether he had ever even met his younger half brother, now a ruthless dictator who has purged dozens of officials while angering the international community by pursuing nuclear weapons and long-range missiles.

Why is Kim important?

The Western-educated Kim was once seen as a dynastic successor for Kim Jong Il, but he fell out of favor in 2001 after being detained trying to enter Japan with falsified travel documents. He said he wanted to take his 4-year-old son, Kim Han Sol, to Tokyo Disneyland.

Kim Jong Nam’s death, which intelligence officials in South Korea have blamed on their enemies in the North, eliminates any future dynastic claim to the leadership role now held by Kim Jong Un.

There are few if any indicators that, at the time of his death, Kim Jong Nam was a threat to the North Korean government — or that he had any future ambitions about ascending to leadership. He was known to travel often, frequenting casinos.

According to some intelligence reports, North Korea’s leader had a “standing order” for years to assassinate his half brother, who once wrote to Kim Jong Un asking that his life be spared.

But the brutal government has a history of purging potential rivals. And historically Korean royals have purged generations of their rivals’ families to prevent challenges.

How sure are we that North Korea ordered the hit?

It’s still not completely clear this was an assassination, or that it was ordered by the North Korean leadership. But Malaysian police are seeking four North Korean men who entered the country last year as tourists. They apparently flew back to Pyongyang after the incident.

The police have arrested four people. The two women were carrying Vietnamese and Indonesian travel documents. A third suspect, the local boyfriend of one of the women, was also held but released this week. A North Korean scientist working in Malaysia was also taken into custody.

Malaysian police also released names and pictures of three other North Korean men who remain in the country. One works for North Korea’s state-run Air Koryo. Another is apparently a high-ranking diplomat in the North Korean Embassy in Kuala Lumpur.

Malaysian police still hope to learn more from the North Korean suspects.

“We hope that the [North] Korean Embassy will cooperate with us,” Malaysian Inspector General of Police Khalid Abu Bakar said this week. “Those who are involved are the North Koreans.”

Malaysian police have few tools to compel the men to talk because of diplomatic protocol. Until the incident, Malaysia and North Korea maintained a relatively healthy relationship. That seems to be fraying in recent days, however.

The South Korean Unification Ministry called the killing a “reckless and brutal case” — and an act of terror.

What does China think of all this?

North Korea shares its northern border with China, an ally on many issues even before its military assistance during the Korean War. The two countries are historically as close — and as different — as “lips and teeth,” John Delury, a professor in South Korea, has said.

China has said it is monitoring the case closely. But officials there can’t be pleased with North Korea’s potential involvement in such a brazen, public act against a man who essentially had asylum in its country.

Pyongyang in recent years also hasn’t heeded Beijing’s warnings about the rapid advancement of its nuclear program and ballistic missile systems. The incident is likely to increase the diplomatic tension between the countries.

Who were those women?

Police are holding two women: Doan Thi Huong, 28, who had Vietnamese travel documents, and Siti Aishah, 25, whose papers listed her as Indonesian. Police asked a court this week to hold them at least an additional week.

Police said that both women touched Kim Jong Nam in the terminal — first the Indonesian, then the Vietnamese. Police said that they have evidence that the women practiced their approach in other crowded spaces beforehand and that the four North Korean suspects in Pyongyang “gave them the liquid,” now identified as a deadly nerve agent.

Abu Bakar rejected media reports that the women were duped in what they thought was a reality television show or prank. He raised his arms to demonstrate how the women carefully walked away from the scene.

“She knew, very well, that it is toxic, and that she needs to watch her hands,” he said of one of the women. “We strongly believe it is a planned thing, and that they are being trained to do that. This is not something, just shooting movies or a play thing. No.”

What’s the status of the investigation?

Basic details about incident remain unclear — including whether the victim was really Kim. He was said to be traveling with official North Korean documents naming him as Kim Chol, a identity akin to John Smith in the West.

None of his family members have arrived to identify him, and the North Koreans haven’t released a DNA sample from a family member — perhaps the half brother himself — to prove a relationship.

Police also won’t say much about the apparent break-in attempt at the building housing Kim’s body.

Abu Bakar told a reporter that the investigation could last years.

“Wait until the trial — then you listen,” he said.

Stiles is a special correspondent.

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