 was killed by a U.S. Secret Service sniper. Investigators say an AR-style rifle found near his body was purchased legally and registered to his father, and that bomb materials were found in his home and vehicle. Crook's phone is being analyzed at the FBI lab in Quantico, Virginia. He worked at a nursing center, and we've learned he was a member of a local gun club. Former classmates say he stayed to himself. CBS News national security contributor Samantha Vinograd.