There are reports that he entered the mall without the rifle, but then had it when he entered Macy’s.
I don't thing those are reports, but interpretations of the terrible quality photos. But, you can see a dark strap across his chest starting at his right shoulder. Very possible he had the rifle across his back. Or, as I mentioned in post #401 (see link there) he could have had a "takedown" rifle under his shirt and pants.
I'm leaning toward a short rifle on his back. At 9:30 pm, not too many people in the mall and most aren't looking at his back. If he had it in a black cloth case, it would be essentially invisible. Just my opinion.