No one else killed because the V in VX stands for Venomous.
It’s super-powerful “snake” poison. Takes 10mg on your skin or 30mg inhaled to be lethal, assuming no atropine injection antidote or life-support breathing provided by a nearby hospital.
A few countries weaponized VX in aerosol form, but as a liquid on a cloth or two (in binary form) it is harmless until mixed and then harmful only to those who receive the liquid via touch or aerosol.
There is one other possibility....
Distilled anise seeds. In high enough concentration, is a powerful nerve toxin.