Morning Joe 09/17/13

Pete Williams: Alexis a man who was mentally 'deteriorating...

NBC News' Jim Miklaszewski and Pete Williams report on Monday's Washington Navy Yard shooting and how alleged shooter Aaron Alexis was able to enter the base, why he chose the building he did and just who he was. PBS' Jeff Greenfield and the Washington Post's Eugene Robinson join the conversation. ... more Duration: {{video.duration.momentjs}}