This is the kind of thing that took place under Saddam Hussein's reign. Although it wasn't reported to the world in real time.
News reports say 29 people have been massacred in Diyala in internal sectarian fighting. Other casualties are reported as the result of a car bomb in Baghdad across the street from the Iranian embassy. But car bombs in Baghdad are like traffic jams on the Los Angeles freeway system now. Commonplace. Almost expected.
Hussein was a despotic dictator. It's good that he's gone. But what's replaced him can hardly be called an improvement.
It seems the Iraqis, like the American-led coalition, are ill suited to enforce civil order. Perhaps Iraqis are incapable of living in a lawful environment unless under the thumb of a powerful supreme ruler.
If the U.S. remains, the killings will continue. If the U.S. leaves, the killings will continue. Killings in Iraq now are, sadly, a way of life.