A federal judge has dismissed criminal charges against a former Blackwater guard accused of firing the opening shots that triggered a massacre of Iraqis in 2007. At least 14 civilians died in the Nisoor Square massacre, including a nine-year-old boy. But the judge dismissed the indictment of Nicholas Slatten after a federal appeals court ruled the charges had been filed after the statute of limitations expired. Prosecutors may seek new charges ahead of the June trial of three other Blackwater guards in the case. The decision comes as an Army sergeant faces a possible court-martial for killing two unarmed Iraqi boys in 2007. At a preliminary hearing this week, military prosecutors said Michael Barbera shot the two brothers as they herded cattle, posing no threat. After an earlier investigation in 2009, Barbera received a letter of reprimand, prompting accusations of a cover-up.