Benghazi had some Syria connection, and maybe some Egypt connection as well, and the US administration has been lying like a rug since the get-go. Maybe they have some good reasons for that; trying to cover up weapons shipments to Syrian insurgents. Although some of them ask for US help, I'd suspect most wouldn't be eager to stain their good Islamic credentials by too much public fraternizing with the Great Satan. So to first order I conclude that we've been shipping arms and other goodies to one or more insurgent groups--and if prior experience is any guide we've sent stuff to enemy groups more than once.
So now there's another poison episode, that seems to kill 1/10 of the victims. Other attacks seem to have killed about 1/3, making this seem more like the Bhopal disaster (1/20 killed). Which suggests that the attack, if it was the government using chemical weapons, wasn't well executed. If rebel groups had the weapons they might not know how to use them effectively. Or somebody might be stirring the pot with something that wasn't completely weaponized. Or this was an accident with stolen weapons.
Although the foreign policy of this administration seems to be managed via Ouija board, I still try to see if there's any sense to this. As plenty of people have already pointed out, we're better off if both groups lose. So there's no sense to intervening unless there's some vital interest at stake. And there is one, that isn't talked about: seizing control of loose chemical weapons. "Punishing" or "sending a signal" makes no sense. We know he had weapons already, and we know he already used them. So where's the urgency? Is something slipping? (And do you trust ∅ to keep his eye on the ball?)