Was he into me or just being friendly?

I got out of my car to go in a gas station & as I'm walking to the door I feel the attractive clerk starring at me (he was smoking a cig to the left of the door) it was really awkward & I felt I personally looked like poo at the time so I just looked at the ground where I was walking. He said "hey" to me so I was forced to look at him & say hello. I see him occasionally when I go to that gas station but we have never exchanged words just kinda looked at each other.

Could he be into me?
Should I maybe flirt a little next time I see him?
Was he into me or just being friendly?
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