Well on this occasion, it's quite clear. Jets (that rebels don't have) were

Bombing the area for days prior to the gas attack. Softens up the area and helps gas spread thru destroyed buildings. Added to evidence he's done it before and the rebels don't have the gas or the means to release it (Yes it can be made pretty easily)
Never gonna get a smoking gun are we?

Posted By: admckechnie, Aug 30, 10:25:05