More info here:
http://www.wltx.com/news/story.aspx?storyid=249667
Lanier said authorities have “multiple” pieces of information indicating there could have been more shooters. She police were searching for a black man between 40 and 50 years old wearing an olive drab military-style uniform and carrying a long gun, Lanier said.
A federal law enforcement official said police killed Alexis, who was armed with an AR-15, a shotgun and a handgun. The federal official, who requested anonymity due to the fluid nature of the investigation, said there is no evidence that anyone other than the dead gunman fired weapons in the attack. The official said investigators were analyzing surveillance video of the shooting.
I would bet that the AR15 will not be confirmed.