Jia Lynn Yang and Matea GoldWashington PostSeptember 20, 2013 USIS, the Falls Church government contractor that handled the background check for National Security Agency leaker Edward Snowden, said Thursday that it also vetted Navy Yard shooter Aaron Alexis for his ­secret-level clearance in 2007. The company, which is under criminal investigation over whether it misled … Continue reading Contractor that vetted Snowden says it also ran background check for Navy Yard shooter