TODAY | September 19, 2013
>>> we have new information this morning on the navy yard massacre and what really happened inside that building. today national investigative correspondent jeff rossen is in washington with more. good morning to you.
>> reporter: hey, matt, good morning. investigators are trying to figure out what made aaron alexis snap and this morning new clues about his troubled mind. authorities say he scratched two phrases into the shot been he used. one said, better off this way t. other said, my elf weapon. they don't know what that means. now, there are beggar questions looming. why was the he ae loued on the base in the first place? aaron alexis was free to come and go at the navy yard . granted special security clearance despite his past, including three run-ins with police and recent struggles with psychiatric issues.
>> there were some red flag , of course there were. should we have picked them up? why didn't we? how could we? all those questions need to be answered.
>> reporter: just last month, alexis complained of hearing voices . it was reported to the local navy officials but never went up the chain of command t. gunman's mother breaking here silence wednesday off camera.
>> i don't know why he did what he did and i'm never be able to ask him why. aaron is now in a place where he is no longer do harm to anyone and, for that, i am glad.
>> reporter: back at the cream screen, investigators have a new account of what happened based on under surveillance video and eyewitnesses. alexis entered building 197 carrying a shotgun in a bag, opening fire from the 4th floor. he then dashed back to the entrants, shot the security guard , took his handgun and kept shooting until police killed him.
>> in watching that video, was there any rhyme or reason to the madness?
>> it's just sheer horror.
>> reporter: d.c. police chief kathy lenear is speaking exclues toively with nbc news. you have not hard for gun control . here is somebody clearly mentally disturbed but he was still able to get a gun what's wrong here?
>> here, we require a background check that includes mental help. but there is that gap.
>> where you can get it somewhere else .
>> where you can get it from somewhere else , literally in this case a ten minute away you can purchase.
>> she wants the loopholes closed.
>> you start thinking about the 12 people that went to work the morning before and didn't come home, it's heart breaking.
>> reporter: one other interesting note here, law enforcement officials tell nbc news alexis created a website with the name mohammed salem. but he did nothing with it and wasn't interested in violent jihad, authorities say it is a complete mystery why he did that.
>> jeff, thanks so much.