I thought it was a brilliant ending as well. For the first time all season, I'm kind of rooting for and cheering along with walt as all of the tension from the heist is released.... And then he shoots a kid. I love how it was edited. Just enough time for me to think, "oh shit what do they do about this kid now" and then his face gets shot. I honestly thought the opening was just to set up the location of the heist.