What killed Kim Jong Nam, who did it and why still not known

FILE - This May 4, 2001, file photo shows Kim Jong Nam, exiled half-brother of North Korea's leader Kim Jong Un, in Narita, Japan. No cause of death has been determined yet for Kim Jong Nam who died last week after apparently being poisoned in a Kuala Lumpur airport, officials said Tuesday, Feb. 21, 2017. (AP Photos/Shizuo Kambayashi, File)

SEOUL, South Korea (AP) — More than a week has passed since the North Korean leader's estranged half brother died in Malaysia, but what killed him, who instigated it and why are still unknown. Malaysian authorities have identified several suspects in the death of Kim Jong Nam, but many questions remain.

WHO DIED: No one disputes that the man attacked at the Kuala Lumpur budget airport on Feb. 13 carried a North Korean passport.

Malaysian Deputy Prime Minister Ahmad Zahid Hamidi says that man was Kim Jong Nam, the eldest sibling of current North Korean leader Kim Jong Un. South Korea, too, is certain the victim is Kim Jong Nam and says the name on the man's passport is a popular fake identity for North Koreans.

Malaysian police still officially use the passport identity, Kim Chol, and have requested DNA from family members to confirm his identity.

North Korea says its confirmation of the man's identity as Kim Chol has been disregarded by Malaysia. A statement released by its embassy Wednesday accused Malaysian authorities of publicizing an unconfirmed identity "alleged by South Korea."

THE SUSPECTS: Surveillance video showed two women walking up to Kim Jong Nam at an airport kiosk, holding something over his face for a few seconds, then walking away. Malaysian police say the two women who were arrested, one Vietnamese and the other Indonesian, knew they were handling poisonous materials and had practiced the attack by approaching people at Kuala Lumpur malls. They said North Korean suspects put the liquid substance on the women's hands before the assault.

Two other people have been arrested: a Malaysian man — believed to be the boyfriend of the Indonesian woman — whose court remand has now expired, and a North Korean man working at a Malaysian company. Malaysian police said Wednesday they also were seeking the second secretary of North Korea's embassy in Kuala Lumpur and an employee of North Korea's state-owned airline, Air Koryo. Four other suspects identified by police have left Kuala Lumpur and are now believed to be back in Pyongyang.

Malaysia has yet to directly name North Korea as the culprit but national police chief Khalid Abu Bakar said Wednesday that "what's clear is that those involved are North Koreans." Police sought cooperation from Pyongyang and the embassy in the investigation, but North Korea has accused Malaysia of colluding with South Korea and describing its investigations as politically motivated.

WHAT KILLED HIM: The liquid rubbed on his face was potent enough to kill Kim Jong Nam before he could reach a hospital. But no one else appears to have been harmed. So what was the poison? Police don't yet know. But certain poisons can be difficult to detect, especially if small amounts are used.

Khalid said the women knew they were handling a toxin and followed precautions as they'd been trained to do: keeping their hands away from their bodies and washing their hands immediately after the attack.

North Korea rejects that any poison could have killed the man and not harmed the attackers.

Some South Korean and other outside experts said the substance might have been a quick-acting nerve agent. They raise a possibility of the use of neostigmine bromide, which Seoul officials said was contained in a pen-like weapon used in a failed North Korean attempt to kill an activist in 2011.

Lee Cheol Woo, head of the South Korean parliament's intelligence committee, said the South Korean spy agency is looking into the possibility that Kim's attackers used something new.

WHY TARGET HIM: Bloodline is extolled in North Korea's foundation myth and is the strongest claim to legitimate rule. The estranged siblings were sons of North Korea's second leader, Kim Jong Il, and grandsons of the nation's founder, Kim Il Sung. By the traditional Confucian value system, the eldest son is the true heir, yet current leader Kim Jong Un is the youngest. So despite Kim Jong Nam's years of exile, many analysts think he could have been killed because he was a potential challenger to power.

Kim Jong Un has executed or purged a slew of high-level officials since succeeding his father in 2011. South Korea has blamed North Korea for Kim Jong Nam's death without providing evidence.

The South Korean spy agency has argued that Kim Jong Un killed a non-threatening sibling out of "paranoia," and the South's defense minister told lawmakers that Kim Jong Un would have been motivated to eliminate the possibility of Kim Jong Nam emerging as an "alternative" to his leadership.

Kim Ju Il, a North Korean defector-turned-activist based in Britain, has told the South Korean media that his group met Kim Jong Nam several times from 2014 and asked him to take part in an exile government, but that he refused. South Korea's Unification Ministry said it couldn't confirm Kim Ju Il's claim.

DIPLOMATIC FALLOUT: Malaysia and North Korea established diplomatic relations in 1973, and Malaysia is one of the few places in the world where North Koreans can travel without a visa. But North Korea several times has questioned the fairness of the Malaysian investigation and the accuracy of its findings.

Malaysia has recalled its ambassador from Pyongyang and summoned the North Korean envoy for an explanation. While experts don't expect a complete severing of diplomatic ties, Malaysia could withdraw its embassy in Pyongyang in retaliation for staging an apparent assassination in its territory.

The United States might also decide to relist North Korea as a state sponsor of terrorism, which would extend the international community's hard-line approach to the North and further reduce the room for dialogue, said Koh Yu-hwan, a North Korea expert at Seoul's Dongguk University.