It is not just any old military installation, it is the headquarters of Sea Operations. I don't know what that is, but considering that it's the Navy it's probably important. CNN's source described it as "one of the most secure buildings in Washington DC."
Aaron Alexis was not a decorated hero, in fact quite the opposite. He was discharged for a "pattern of misconduct" which may or may not be related to two separate gun-related incidents, one in Ft. Worth and one in Seattle. On the other hand, they are quick to point out that he was not dishonorably discharged. His was an "other than honorary" discharge. Whatever it was did not prevent him from being hired by a Navy contractor. Supposedly Alexis' area of expertise was "computer security."
There are reports coming out now that he may have been disgruntled over not getting some sort of benefits to which he was entitled, or at least believed he was.
Then there are all these people in Ft. Worth who know him as a soft-spoken Buddhist and co-owner/waiter/friend of the family at a popular Thai restaurant. One of the local reporters even knew him. He also spoke Thai.
Yeah, this just gets weirder and more interesting.