Nightly News   |  September 16, 2013

Who was Navy Yard shooting suspect Aaron Alexis?

Authorities believe Aaron Alexis acted alone when he fired upon the Washington D.C. Navy Yard.  Learn more about the 34-year-old man’s background. NBC’s Pete Williams reports.

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This content comes from Closed Captioning that was broadcast along with this program.

>> now the latest on this investigation. what we know about this gunman. our justice correspondent pete williams has been reporting the story all day. he's in our d.c. newsroom for us this evening.

>> reporter: in the chaos after the shooting was reported police thought more than one gunman might have been responsible. tonight they say they believe shots were fired by one man who apparently had a grudge against the navy.

>> we have an active shooter on the fourth floor. i will get you an update on the building location. several victims now.

>> reporter: surveillance video captured around the time of the shooting appeared to show three people with guns drawn prompting an all out search for possible accomplices.

>> right now we have multiple pieces of information that would suggest we have at least two other individuals seen with firearms.

>> reporter: late in the day investigators believe the shots were fired by one person acting alone who was killed by responding police. authorities say the suspect, aaron alexis , age 34, moved to the washington area four months ago from ft. worth, texas. a navy petty officer specializing in electronics, he served as a naval reservist. he had a job working here as a civilian contractor, but investigators are looking into claims that he recently lost that position which they say may have set him off. the fbi is asking for public help in learn ing more about what his motive may have been.

>> no piece of information is too small. we are looking to learn everything we can about his recent movements, his contacts and his associates.

>> reporter: federal officials say they believe he arrived carrying a shotgun and apparently picked up and then used other weapons from law enforcement officers he shot.

>> we heard very close to us a gun blast. and actually we saw bullet holes in the wall above us.

>> reporter: officials say he may have entered the building today using someone else's i.d. badge the badge owner was questioned but officials say they do not believe he had anything to do with the shooting. the owner of this thai restaurant in ft. worth said he was the roommate and best friend of alexis .

>> we lived together. we shared a house. we'd go out and party. we'd do a lot of stuff together.

>> reporter: friends and government officials say alexis worked as a computer consultant in ft. worth before coming to washington . a ft. worth police report said he was arrested three years ago for firing a bullet at his apartment building that went into the unit above him. he claimed it was an accident while cleaning his gun, but he was later evicted. friends in texas describe him as a peace ful, practicing buddhist. police in washington arrested him nine years ago after he shot out the tires of a car used by workers who parked near his house. a police report said he did it during what he called a blackout fuelled by anger.

>> learning more by the hour. pete williams with more on the investigation from washington . thanks.