Transcript for Half-brother of Kim Jong Un believed to be killed by deadly nerve toxin

Tonight we are learning more about the chemical agent used in the middle of a busy airport authorities now believe the world's deadliest talks and was used to kill Kim Jong owns half brother. It happened as passengers were seated and walking nearby investigators say this surveillance chose to women using get VX nerve agent rubbing it on the man's face. The BX nerve agent is colorless odorless and authorities say one of the women became violently ill her self moments after. Here's our chief foreign correspondent Terry Moran taking a step by step tonight through that surveillance. The bizarre assassination call them pours busy airport now classified as a terrifying weapon of mass destruction attack. After Malaysia's police chief revealed today. Stunning a toxicology results. In recent years are. XV it'll be mix three eggs or another agent it reduces chemical weapon. It's one of the mark lethal. Creations that man has ever ever come up with. The X is odorless and tasteless. A tiny amount will trigger uncontrollable muscle contractions causing first confusion drowsiness nausea before leading to death or paralysis. And it killed Kim Jong Nam half brother of North Korean leader Kim Jong-un in minutes. Just every so otters into the airport a woman lunges at him from behind rubs his face for an instant and moves quickly away another woman was also involved. Kim immediately reports to airport authorities gestures to his face and soon collapses. Experts say the assassins were risking their own lives by handling of the excel open and thinks about held the rag to rethink some sort of rubbed in. That individual is is putting themselves in them Mattson in harm's way. Both women survived no one was vomiting after the attack. The airport now being decontaminated. DX can last for days the brazen assassination the latest in Kim Jung learned bloody reign. Taking out his estranged half brother. A possible rival. And his regime estimated to have up to 5000 tons of chemical weapons. And Terry Moran for this live from London tonight and Terry now that investigators know what killed this man will they be able to. Trace the source of those chemical weapons. There's a very good chance of that David. Teams of chemical weapons specialist from around the world and I'll take a look at the swabs taken from Kim Jung on eyes and face. And they'll look at that. Chemical fingerprint and intelligence gold mine now see how. How it was made they may get a chance to see where it came from this may be a real window and the North Korean capabilities. Good going our chief foreign correspondent Terry Moran tonight Terry thank.

This transcript has been automatically generated and may not be 100% accurate.