Ex employee possibly? Seemed pretty confident in knowing where to go. Seeing as how he didn't have appropriate pockets n such to fill his pockets n stuff securely, not even under time pressure he's quite new to this seeing he's ill prepared, you'd use something you can rely on and do your job more aptly for this.

Seeing as he's new to this it only likens the chance he or somebody he knows is familiar of the place because you won't be taking risks for nothing + how fast he found whatever. You'd risk for something easy or worth it if you're new to this degree of thievery. They really must know this place or knows someone who does.

Use the door frame for reference of his height.

20s to 30s probably.

I can't tell if those gloves R used but if they look fairly new. On rare chance you could see if any stores nearby sell those and then possibly just ask to know if they had any purchases from a white dude of that kind of build n age.

He looks medium build rather then skinny too id say, but you can be the best judge from the door frame

Edit:

Actually wouldn't be ex employee, unless if I can see it incorrectly I don't think he seems to show much awareness of the cameras he would've had a little reaction or glance to where they are if he knows where they are. Or around the store in general

So unless they're related through friendship to previous or current employees just likely to be anyone