Is there a second shooter?

11:44 AM ET Mon, 16 Sept 2013

If there is a second shooter it does imply some sophistication or knowledge of the surroundingsat the navy yard, says Michael Leiter, NBC News terrorism analyst, who provides insight on what's likely going on behind the scenes. Law enforcement agencies continue to investigate what happened, while the Navy reports there were no additional shots fired since the shooter was neutralized, reports CNBC's Eamon Javers.