Jeremy Scahill is the author of Blackwater, the Rise of the World’s Most Powerful Mercenary Army. He describes the Sept. 16, 2007 incident in which Blackwater guards killed 17 civilians in a Baghdad square. The Iraqi government demanded that Blackwater leave the country, but all that happened was a three-day pause, because US operations depend on Blackwater. Scahill says a US military investigation determined that all 17 killings were unprovoked. But US actions have kept the killers from prosecution and “they’re walking around as free people.” Of the hundreds of thousands of contractors who have worked in Iraq, says Scahill, only two have ever been charged with any crime: One for having child pornography on his computer at Abu Ghraib, and the other for allegedly stabbing another contractor.