VX nerve agent, a chemical the United Nations classifies as a weapon of mass destruction, was used to kill the estranged half-brother of North Korean leader Kim Jong Un in a bizarre murder in Malaysia last week, police said on Friday.

Kim Jong Nam was killed on Feb. 13, shortly after being assaulted at the airport in the Malaysian capital, Kuala Lumpur, by two women who wiped the chemical on his face as he prepared to board a flight to the Chinese territory of Macau.

… North Korea is believed to have a large stockpile of VX that can be easily made with low prices, according to Rohan Gunaratna, an expert on terrorism at the S. Rajaratnam School of International Studies in Singapore.