Why couldn't he pull it off. Guns are easy to make. Like I already mentioned, there is a whole city in the Philippines that is known for making black market guns mostly in sheds with just hand tools. http://www.youtube.com/watch?v=sDppu3Mcj6E
Then there's the simple AK which is mostly stamped metal, designed to be easily made in small shops. Lots of people have made their own. You can find a lot of Youtube videos on how to make an AK.
http://www.youtube.com/watch?v=sDppu3Mcj6E
http://www.youtube.com/watch?v=xO68T2RcD-Y
etc.
Now with 3d printers becoming more common, people will just be able to print guns. http://www.extremetech.com/extreme/133514-the-worlds-first-3d-printed-gun
Except you'll get caught. It would be dead simple for the cops to do that too. If you ponder that for a moment you'll see why this is obvious.
