There was apparently a no cameras or phones policy at the concert, which Carter followed until the very end of the show, when he couldn't resist getting just one quick photo. On Reddit, he said:
I felt like I was stealing it at the time, but at this point I just feel lucky and honored to have been there and to have taken a picture that makes one of my heroes look exactly as I always wanted him to. Never would have imagined it would be one of the last.
No one did.