According to documents reviewed by The New York Times, State Department investigator had already begun probing Blackwater a short time before the infamous Nisour Square shooting in 2007. But the probe broke down when Blackwater's top guy in Iraq threatened to kill the lead investigator, suggesting, not improbably, that amid the anarchy of Iraq it could be easily covered up as just another moment of sectarian violence or a terrorist attack.

From the Times ...

Just weeks before Blackwater guards fatally shot 17 civilians at Baghdad's Nisour Square in 2007, the State Department began investigating the security contractor's operations in Iraq. But the inquiry was abandoned after Blackwater's top manager there issued a threat: "that he could kill" the government's chief investigator and "no one could or would do anything about it as we were in Iraq," according to department reports.