Why is the Syrian Baath Party committing crimes against humanity? Because it has not succeeded in putting down the 14-month-old rebellion against one-party dictatorship by other means. They began by putting snipers on buildings above city squares and just shooting 10 demonstrators in each population center every day. The point was to raise the cost of protesting, to make people wonder if this would be their last demonstration. When the brave protesters nevertheless insisted on continuing to come out, and when the regime lost control of some city quarters to armed defectors from its own military, the regime actually sent in tanks and artillery to pound the rebellious quarters (as with Baba Amr in Homs), despite the inevitable loss of civilian life.
But that use of armor against city quarters did not succeed in quelling the rebellion, either. So the regime has gone to the next step. It is using shabiha death squads to simply kill the unarmed protesters, including women and children, and giving the death squads cover with artillery and tanks. The death squad technique is typically the death rattle of a regime.