Federal authorities arrested and charged a Sterling, Virginia, man with attempting to obstruct a terrorism investigation on Friday, accusing him of acting in a manner that was "indicative of an individual planning and researching how to conduct an attack," according to records filed in federal court. The filing says Sean Andrew Duncan, who moved to Sterling from western Pennsylvania in June, had owned a phone that revealed prolific research into materials relating to the Islamic State, terrorist attacks, weapons, surveillance tactics and body armor.