"They said the Marines opened fire on houses. "I saw a soldier standing outside a house and he opened fire on the house," said one resident, who did not want to be identified..."
That's a substantial difference than going into houses firing at "point blank" range in a "cold blooded fashion".
We do not have all the facts yet, so even what I have to say is speculation - but how many times in the past three years have our troops "fired" at some civilian looking target, BECAUSE THEIR WAS GUNFIRE COMING FROM INSIDE and those firing were using the civilians present as their "shields" and as culpable deniability "evidence" when the shooting was over - "see, the Americans were just shooting at "civilians".
Is that what happened? No idea. But that has happened many times over in this war.