WASHINGTON (AP) — In trying to identify who was behind a major breach of classified U.S. documents, federal agents and journalists had access to online clues that led to a 21-year-old Air National Guardsman with interests in gaming, guns and religion. Jack Teixeira, an airman from Massachusetts, was arrested Thursday in connection with the leak investigation. He will be charged with the unauthorized removal of classified national defense information. The case underscores the challenges the U.S. and other governments in keeping secrets and staying ahead of breaches in an era of omnipresent data. And it also shows the apparent power vested in a junior U.S. employee.