Kim Jong Nam, the half-brother of North Korean leader Kim Jong Un, was killed by a highly toxic VX nerve agent that the United Nations has classified as a weapon of mass destruction, Malaysian police said Friday. Earlier this month, Kim was at the Kuala Lumpur airport when he said a woman grabbed his face and sprayed him with some sort of chemical; he died from a seizure on the way to the hospital. Authorities say a preliminary analysis of swabs taken of his face and eyes shows ethyl N-2-Diisopropylaminoethyl Methylphosphonothiolate, the most potent of all nerve agents, which is lethal after just a fraction of a drop is absorbed through the skin. Previously only seen in chemical warfare, the Centers for Disease Control and Prevention says exposure to the nerve agent can lead to convulsions, paralysis, and fatal respiratory failure. The police have said two attackers rubbed a liquid on Kim’s face before they fled and washed their hands.