I some immediate thoughts about this. First, it seems that because it is ongoing and therefore quite dynamic, it is possible that some or most of the information being disseminated is not accurate. And the area where the shootings occurred is an active crime scene, so it's likely that some information is simply not being made available because of the investigation that is underway. Plus, there are other military facilities around the area of the Yard, including the Pentagon. If there are multiple shooters loose, and they have other ideas, then the security at all of these other facilities is already ramped up.
The obvious question being asked is who these people are. Are they disgruntled military personnel? Is this a terrorist act? If they are not military, how did they get onto the property? It is supposed to be a secure facility. Military installations, as a rule, are not supposed to be easy to get into.
While there have been so many mass shootings and other incidents over the past year or so (Sandy Hook and the Boston Marathon come to mind immediately, as well as a shooting at the Quantico Marine base that also occurred), this one sticks out because of not only the time of day, but the number of victims that, at least as of now, are being reported. It's really disturbing.
I'm already hearing that, with respect to the ongoing argument between those who wish to restrict the rights of gun owners and others who believe that that owning guns is a basic right because of the existence of the Second Amendment, that this incident is "the straw that broke the camel's back." Maybe this is true, but I'm not so sure. I say that because what if this was a terrorist attack? Until this is resolved and the other shooters - if they are indeed out there - are caught, there is absolutely no way to know what the reason for this was, how their weapons were obtained, and how they were able to get access to the area where the incident occurred.
My feeling about this is simply to hold judgment until this is resolved and all of the facts are collected. And pray for the victims. It's that simple