Why was no one else killed. ?
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.
Supposedly it was applied to him by a rag and not sprayed in the air. He'd be the only one affected, though some reports say one of the suspects arrested in the murder is suffering from some effects of VX.
It wasn’t in the form of gas.