The initial reports I read said he had approached airport security seeking help. Just seems improbable to me that if the stuff, no matter how viscus or how cut with filler could have been completely wiped away within a few seconds so as to not contaminate and kill others trying to render assistance. I've been through KUL several times but not through the budget terminal, its a beautiful airport and very busy, just can't see how a chemical agent with the lethality of VX could be used in that crowded place to take out just one individual without a lot of collateral damage.
Unfortunately don't think we will never know the entire truth. Knowing that part of the world as I do I'd suspect that if the North Koreans are sophisticated enough to pull off a targeted VX attack, they are also using the less sophisticated cash to influence how this story is being reported by the government there...
At a LD50 of ten milligrams, (one 100th of a gram)
https://en.wikipedia.org/wiki/VX_(nerve_agent) a rag wiped on the skin of the face and/or neck would likely do it. The stuff is liquid, the consistency of motor oil and is a transdermal poison. It isn't like Sarin gas (low volatility/high latency), and would be ideal for just such a hit, without exposing a large number of others (provided they didn't touch his skin where the VX had been applied). While it can be inhaled, the skin contact would be more effective. It takes about five times as much inhaled, and the first reaction unaffected people have (in general) to someone collapsing is to get back out of the way and give them some air...with low volatility, that exposure would be limited.
The victim would know he'd been poisoned and seek help. Early symptoms of percutaneous exposure (skin contact) may be local muscular twitching or sweating at the area of exposure followed by nausea or vomiting. He'd look sick, facial sweating, twitching, and sick to his stomach.
Collateral lethality would depend on cutaneous exposure, and that would generally be unlikely except for possibly guards or EMS; the latter commonly wear gloves to protect from serologically borne diseases.
If you think about putting motor oil on a shop rag or sponge and sneaking up behind someone with the sponge/rag in a ziplock or similar bag, opening the bag and smearing it on them, stuffing the rag back in the bag, sealing it and bugging out. Yeah, it's do-able. Discard the bag, shuck the gloves to protect the operator (double gloved, one set at a time), and walk out. The stuff likely ended up in a trash can somewhere in a sealed bag. Dump the first pair of gloves ASAP, the next pair soon after, and common contact surfaces would be clean--no collateral exposure, no directional trail to follow.
Just think about how you would do it if you had to, and the method becomes more apparent.
