 FBI lab in Quantico, Virginia, for analysis. The FBI says the gun was purchased legally, it believes, by the shooter's father. Rojek identified it as an AR-556, which is an AR-15-style rifle. The cell phone, though, is an urgent focus for investigators. NPR's Ryan Lucas reporting. The Republican National Convention officially kicks off today in Milwaukee, Wisconsin. As NPR's Young-Yoon Han reports, former President Trump is already in the city and ready for the event.