Just happened today. First time it's happened that I've noticed.

I was looking at some t-shirts in a hidden corner of the store. 
Woman maybe 30-40 years old in plain clothing suddenly appears not more than a few feet away, also looking at the same shirts I was just looking at (Red flag #1)

Immediately once I spot her I walk away to a different section of the store to look at pants. I look there for about a minute, and then happen to turn around and glance back in the direction of which I just came from. 

I see her looking straight at me for a few seconds. Hard to explain the look she was giving me, but her eyes were squinting a little bit like she was curious of my intentions. Have no idea what caused her to all of the sudden start watching me like that.

I'd say it's because of my skin color, but there were lots of other colored people around so what the hell was her problem? She was an African-American woman too. Was she loss prevention or was she just a weirdo? 

Anyway, I gave her a pretty menacing look before we both broke eye contact. That's why I want to know if I'm being an asshole for giving her the stink eye for watching me like that. Nothing else happened after. Didn't see her again. Cannot describe how weird and uncomfortable I felt during those moments. 