Whoever did it, I very much doubt it was Assad's forces. They don't need to. They wouldn't want to, because it doesn't help them in any way, but hurts them. They are already winning their war anyway. For them to have done so is about as unlikely as for Mr Obama to cross the floor and join the Republican Party or sign up for the KKK.

As for who did it? That's easy. He who gets what he wants as a result of doing it did it! And that could be any one of: The USA, the UK, France, Turkey, Israel, and the various foreign-backed "rebels" and jihadists that the American/UK/Israeli axis has been supporting and supplying for 2 years now for the purpose of overthrowing the government of Syria. Any one of them might have done it...with possible collusion and assistance from one or two more of them.

It's another utterly phony "false flag" propaganda exercise to provide the USA and the UK with another spurious reason to go to war. When you've already caused the deaths of hundreds of thousands of civilians across the Middle East (if not millions), to pretend moral outrage over the deaths of a few hundred more is the height of hypocrisy.