Written by Aric Toler, Christiaan Triebert, Haley Willis, Malachy Browne, Michael Schwirtz and Riley Mellen The 21-year-old National Guard airman was frantic as he joined a call with members of a small online gamer community that has improbably ended up at the center of a federal investigation into a major US security breach. It sounded as if the airman, Jack Teixeira, was in a speeding car, said a member of the group who uses the screen name Vahki. “Guys, it’s been good — I love you all,” Teixeira said, Vahki recounted. “I never wanted it to get like this. I...