disorder. it is thursday, september 26th. >> announcer: from abc news this is world news now with john muller and diana perez. good thursday morning, everybody. we're learning much more about the deadly attack in the navy yard. >> it's showing the gunman in real time roaming the hallways. here's pierre thomas. >> reporter: this is aaron alexis armed with a sawed off shotgun hunting innocent victims. it started as a routine monday at the navy yard. alexis shows his pass and is waived in by a security guard just before 8:00 a.m. surveillance cameras capture him driving into a parking garage and moments later walking in through the front door of building 197. he's working there as a civilian contractor. there's no metal detector, no bag check. we next see alexis armed with a shotgun peeking around corners, checking doors, looking for