4:00pm - Good news: MedStar Washington Hospital Center says two of three victims are in surgery, but will recover. Third will not require surgery, and is also expected to fully recover. They do not expect any more patients from the scene.
3:58pm - Daily Beast has already run an op-ed by David Frum using today's mass shooting as reason to argue in favor of restricting American's Second Amendment rights.
3:54pm - CNN just "broke" the news identifying the shooter as Aaron Alexis, more than an hour after other outlets broke the news.
3:40pm - AP speculates that the the dead shooter is from Texas, has "a criminal record there and to be a holder of a concealed carry weapon permit."
3:36pm - NBC 4 reports the dead shooter, Aaron Alexis, was arrested in 2010 for illegally discharging a firearm.
3:23pm - Breitbart editor-in-chief Joel Pollak writes: "I have spent some time at the Navy Yard, observing a military trial when I was in law school. The compound is large and well-guarded, and an important landmark in southeast Washington, DC. Navy personnel take security very seriously and consider each separate building to be a "ship"--i.e. stairwells are referred to as "ladders," and so on. The Navy Yard has a long and storied history and it is terrible to know that it has now been marred by such a terrible event."
3:10pm - NBC 4 says security video shows shooter entering building with a shotgun. Police believe he might have stolen a semi-automatic 9MM pistol from the first security guard he shot with the shotgun. He then might have shot another guard who would have responded carrying a AR-15 assault rifle, and then the shooter grabbed and used that. This is all speculative; what the media is reporting what the police are investigating.
3:10pm - DC Nationals cancel tonight's game. Rescheduled for tomorrow afternoon.
3:07pm - Earlier this morning on CNN, anchor Carol Costello apparently forgot about the 2009 Fort Hood massacre. "This seems so unusual to me that a gunman could create this kind of havoc at a U.S. military facility," Costello said. She then asked, "Have you ever heard of it happening before, Brian?"