Mall of America would be an attractive target for two reasons:
1) Lots of unarmed, unaware targets.
2) Minneapolis has a very large Somali Muslim refugee population. In fact, two of the Somali pirates depicted in the movie
Captain Phillips were played by actual Somali immigrants; both of whom "hailed" from Minneapolis. I'm sure when all these Somali refugees were allowed to emigrate to the US they did not leave their ideology in Africa...
I wonder if they were allowed to bring their full-auto AK's with them when they fled Somalia...