As the investigation continues, the mystery of just what happened to the half brother of North Korean leader Kim Jong Un as he waited for a flight in a Malaysian airport only deepens. Was Kim Jong Nam poisoned? Are the two female suspects trained killers or dupes? How can we be sure that North Korea, which seems the obvious culprit, was even involved?

South Korea’s National Intelligence Service — no friend to Pyongyang — and eager reporters across Asia have assembled a dramatic, almost cinematic profile of the last hour of Kim’s life. But there’s still a surfeit of unanswered questions.

Here are a few:

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WAS HE POISONED?

This one could be answered fairly soon.

Kim complained of being sprayed in the face with some sort of chemical before he died. Presumably Malaysian authorities’ autopsy, which has been completed, will determine whether poison killed Kim, and, if so, what kind.

A big question is how possible killers would have managed to quickly inflict a fatal chemical dose on someone in the middle of a busy airport.

South Korea’s intelligence service says Kim almost certainly was poisoned, but it’s unclear whether a needle or spray was used, and the spy agency didn’t elaborate.

One possibility for the poison is neostigmine bromide, which South Korean officials said was contained in a pen-like weapon used in a failed North Korean attempt to kill an anti-Pyongyang activist in 2011.

Or it could have been cyanide or sarin gas, according to a Seoul university professor who didn’t want to be identified because Kim’s autopsy results weren’t out yet.

Sarin gas was used in a deadly attack on Tokyo’s subways in 1995.

And if it turns out that Kim wasn’t poisoned? Expect furious media backtracking, and flustered explanations in South Korea from the spy agency.

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WAS IT REALLY NORTH KOREA?

North Korea, of course, is the easy answer.

South Korea’s spy service considers the North the bogeyman and almost immediately, in a private briefing to lawmakers in Seoul, pointed the finger at North Korean agents for the death, saying that Kim Jong Nam had been targeted for five years because of Kim Jong Un’s “paranoia.”

Most news media have run with this, but, so far, Malaysian officials have provided no solid links to North Korea.

When asked Thursday if North Korea was behind the murder, Malaysian Deputy Home Minister Zahid Hamidi said, “That is speculation.”

This doesn’t mean that North Korea couldn’t have orchestrated such an attack. It does fit a certain profile: North Korean agents have, at times, run wild in South Korea, killing defectors, sometimes with poison, and critics.

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WHO ARE THE ARRESTED WOMEN?

The two women arrested in connection with Kim’s death were spotted on surveillance video at the airport where Kim fell ill.

Both are reportedly in their 20s. One held an Indonesian passport. The other had Vietnamese travel documents and was seen in grainy photos waiting for a cab while wearing a white jumper emblazoned with “LOL” — internet-speak for Laugh Out Loud.

But their possible involvement in Kim’s death is still unclear.

Were they simply in the wrong place at the wrong time? Were they North Korean agents, maybe even North Korean nationals using false passports? Kim Jong Nam, in one of his lowest moments, was humiliated while trying to sneak into Japan to visit Disneyland — with a Dominican passport.

Police are trying to verify if the women’s travel documents are genuine, according to the Malaysian minister. Police said they have also arrested a third suspect, a Malaysian man thought to be the boyfriend of the suspect with an Indonesian passport.

If this was a carefully planned assassination — years in the making, as South Korean intelligence claims — it begs more questions: Would North Korean agents be so easily arrested — one of the women was picked up back at the airport, two days after Kim’s death? Would they really take taxis from the scene of the crime?

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ARE OTHER EXILED NORTH KOREANS IN DANGER?

South Korea’s government said it was boosting security for high-profile defectors in the South, many of whom already have police protection.

Kim Jong Nam was long protected in his Macau base by China, according to Seoul’s spy service. South Korean officials say he leaves behind two sons and a daughter between two different women living in Beijing and Macau.

Ha Taekeung, a South Korean lawmaker and North Korea human rights activist, said in a radio interview Thursday that Kim Jong Nam’s son, Kim Han Sol, could be in danger because he knows sensitive secrets about Kim Jong Un’s personal life.

Kim Han Sol, who lived with his father in Macao, referred to Kim Jong Un as a “dictator” in a 2012 interview.

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WHAT WILL CHINA DO?

China, North Korea’s most important ally, has said little officially about the death. Beijing reportedly saw Kim as a potential leader should North Korea’s government ever collapse.

An editorial in Global Times, the ruling Communist Party’s English-language newspaper, said Thursday that China would offer condemnation if Kim was found to have been assassinated.

“Regardless of how intense a country’s political struggle might be, there is no doubt that it should never rely on assassination methods as means for its advancement,” said the editorial. “Although a final conclusion has yet to emerge regarding Kim Jong Nam’s sudden death, speculation remains sharply pointed at Pyongyang.”