Horrible images, and the unfortunate cost of war, something the Gulf Arabs, Turkey and the Syrian rebels should have thought of before launching a violent conflict against the incumbent government of Syria.
What did they think would happen? That Assad would just say sorry and hand over power? Assad had made some concessions in negotiations, and while they were certainly not enough, they should have been accepted and used as a basis for greater change over the long term, within the system.
Violent uprisings have a cost, especially civil wars, and the responsibility for the cost of the Syrian civil war lies first and foremost with those who supported violence against Assads regime as a political tool.