Is it normal guy gives me attention but then doesn't?

There's this guy at my work who when he comes into work, comes up to me and asks me how I am, what's been going on and then tells me how his day went and asks if there's anything new. We talk for about 2-4 minutes (when he should be in his area) and then he heads over to his area.

Then when I'm walking to the copy/fax machine and sometimes run into him, he doesn't say anything at all and just smiles instead.

Then, when I leave. I say good night and he just says "have a good night", smiles and then I leave. I once ran into him outside of work and he talked to me for a good 10 minutes on a check out line/after we had both been done and he asked what I was up to.

He also once said "being single is sad" to me.

Is this normal chit chat or does he like me? Turns out he has a girlfriend now as of last week. I heard the details from one of his male buddies at the store and says he met her in his college class and she started flirting with him, he didn't like her at first because she's too much of a tom boy (apparently) but then he went out with her.

is it normal for a guy to do this?