Simply a natural reaction. Didn't know the guy and had no idea what his intention might be. I don't profess to be Marshal Dillon so I plan to be a step ahead whenever possible.
I noticed a fairly large black guy wearing sweats reach for something on an upper shelf. As he did so, his shirt came up and his pants sagged and there was his S&W Bodyguard in a Kydex paddle holster
If I ever expected to see someone carrying in a paddle holster with sweatpants in would be in Walmart --LOL
It's hard to ccw with sweatpants or athletic shorts, I'm surprised the paddle didn't make his pants sag noticeably.