Washington Navy Yard shooting: amoklauf or terror?

There's still a lot of confusion at the scene of a mass shooting this morning on the grounds of the Washington Navy Yard. All we really know is that some people were shot and some of them are dead. The big point of confusion as I write, as is often the case, is the number of shooters. Descriptions from witnesses differ enough (on race, clothing, weaponry, etc.) that investigators must continue to entertain the possibility of multiple attackers. The more people were involved, the more likely that this will prove an act of terrorism rather than the amoklauf of, say, a disgruntled employee or an isolated nut. Even if there proves to have been a single shooter, the choice of target makes it impossible to dismiss terrorism as a motive at this time. There's little point to speculating until we learn more, but I'll be back when we do.