Kim Jong-nam, the estranged half-brother of North Korean leader Kim Jong-un, died after being attacked with the banned nerve agent VX at Kuala Lumpur International Airport on February 13. Malaysian authorities said two women approached him in the check-in hall and wiped chemicals on his face. He sought medical help, suffered convulsions and died on the way to hospital. He was travelling on a passport bearing the name Kim Chol.

Malaysia’s police chief said preliminary toxicology tests detected VX in swabs from Kim’s face and eyes. VX is an exceptionally potent, persistent nerve agent that can be absorbed through the skin. It is banned under the Chemical Weapons Convention, which North Korea has not signed. Authorities said they were investigating how it entered Malaysia.

The identification of VX raised questions about safety at the airport, which had gone about 11 days without decontamination. Authorities said they intended to clean areas visited by the suspects. Police reported that no one else had fallen ill, although the police chief said the two women had suffered vomiting. Toxicologists questioned how the women could have handled the substance and left the scene, while police said they had been instructed to wash their hands afterward.

Malaysia accused North Korean agents of directing the attack and detained several suspects, including the two women, one Vietnamese and one Indonesian. Investigators also sought other North Koreans, including an embassy official. The Vietnamese suspect’s family said she must have been deceived; Malaysian authorities disputed that account.

The killing sparked a diplomatic dispute. North Korea denied responsibility, challenged Malaysia’s investigation and accused it of fabricating evidence. It also blamed Malaysia for the death and did not acknowledge that the dead man was Kim Jong-nam. Malaysia warned that it could expel the North Korean ambassador over his accusations.

Kim Jong-nam, the eldest son of former leader Kim Jong-il, had once been considered a possible successor but lived abroad after falling out of favor. He later criticized North Korea’s policies and hereditary succession. The reports cited estimates that North Korea held thousands of tons of chemical weapons and had the capacity to produce substantial quantities, including agents such as VX.