Skylar and Walt Jr. in the bags, due to a meth lab explosion (make sense given the HazMat suits of the people sifting through the mess) leaving Walt a fugitive. You didn't see the third body bag b/c it would have given it away who was under the other two, or did the baby escape harm? This leads Walt back to "needing" Jesse, which is the reason he hasn't left him in the past.