One key revelation: it is not clear whether Aaron Alexis was armed with an AR-15 or not
Also, no clear motive has been established.
A law enforcement official says it was a 12 gauge shotgun, which he assembled in a men’s room once he gained access to the facility:
WASHINGTON — Navy Yard gunman Aaron Alexis cleared a security checkpoint with his contractor ID and carried his shotgun, unassembled, into Building 197 within minutes of starting his bloody rampage Monday, federal investigators said Tuesday.
Investigators revised and refined the sequence of events at the Naval Sea Systems Command headquarters that left 13 people dead, including Alexis, who was shot to death in a showdown with police.
A federal official said the 34-year-old contractor recently paid about $540 to buy the 12-gauge shotgun and ammunition at a gun store in Virginia and took them to the Navy Yard Monday morning.
The official, who spoke on condition of anonymity because the criminal investigation is continuing, said investigators believe that Alexis stopped in a men’s room and assembled the law-enforcement style shotgun, then proceeded to a spot on the third or fourth floor of the building that overlooked an interior atrium.
The latest scenario contradicts an earlier version in which officials believed that Alexis may have shot his way into the building because of the location of two victims just outside the building. But it is now believed the victims may have moved there from another location.
Contrary to earlier reports provided by law enforcement officials, Alexis was not believed to be in possession of an AR-15 rifle, the official said.