a massacre claimed 12 lives here. the gunman who knew he was disturbed. >> the latest today, the navy yard will be closed to all except investigators. chuck hagel was here last hour, placing an a wreath in honor of the dead and wounded in building 197. >> that's exactly where the military contract worker and former navy reservist we now know as aaron alexis opened fire, shooting down colleagues with a shotgun, not a semi at maut ick rifle as first believed, though. we're also learning that alexis recently had sought help at two veterans hospitals, reportedly for psychological aissues. we're joined now by our justice correspondent evan perez with the latest on this investigation. get us up to speed on these changes in the details. clearly when these things start to roll out, evan, there are