How fast does sarin act? Is it a thing where the person who disperses it would have to be protected or else they would die before they could finish the job - like if they were in a crop-duster? How likely is it that if the rebels used sarin they had delivery systems from somebody higher, like Iran or (gag) Obama?
For Sarin they’d have to be protected and also carry antidote for emergencies. The antidote is jumbo shots of atropin and doesn’t work all that well.
Often Sarin is laid down in binary form, that is, the load is harmless until it hits the target. But even then, the wind can turn on you.