I worked for a while on the checkouts of a small Tesco in a small town. As you can guess, pretty much everyone that shopped there would be regulars and lived in the town. You'd see them often, get to know them a bit etc.
Except this one guy.
He'd come in several times a week, only ever buying a few bits. There was something 'off' about him. I can't put my finger on it really.
He wasn't really rude to people or angry or sweary or anything, he was.just 'off'
He'd plonk his items on the belt and kind of just stand there. No eye contact, no chatting, no "Hiya, how are you? Having a good day? Ain't the weather horrid" etc etc.
I'd say,
"Hi there how are you? Need help with packing?" Or whatever. The most you'd get is,
"Hi, no you're ok thanks."
The he'd pack his stuff into an empty product box he'd take from a shelf somewhere and leave.
If you were stacking shelves when he came in, you'd kind of move, because he wouldn't think anything of moving your stock cage if it was in his way, like he didn't even really notice other people around him.
If he wanted eggs, for example, he'd walk in the doors, through the checkout backward, moving through people like a snake through a bush, straight up the aisle, push a stock cage or someone's trolley out the way, grab his eggs and back to the till.
Most people kind of amble, look around, spend minutes picking biscuits.. he didn't.. you'd see him enter, go round and be at your till in minutes.
No trolley or basket, No bags either.. he'd take empty boxing from a shelf and put his bits in that instead.
He wore like army trousers and boots and walked like he was a soldier in a perpetual rush. he was so we nicknamed him sarge. (Bit rude of us I guess)
I know he was probably just on a rush, shopping isn't exactly a social thing for some people, but yeah, he had a vibe which I'm not explaining well. It's been a decade since though and I can still remember the jangle of his keys where they were hooked to his belt as he walked.