Silly question?

Okay, this is a little bit dumb, but I would like to hear some opinions.

A few days ago I suddenly found myself attracted to a co-worker who's in another department down the hall. I would smile and say hello whenever we passed. My smiles were warm and I extended the eye contact for a second or two. He seemed to reciprocate the same vibe I put out. We haven't actually conversed, just a bunch of hey how are you's...but, it was mostly about the look, the vibe, my smile, and the mutual extra eye contact.I assumed he was into it. I'm in my mid 30's, he looks 40-ish give or take, bottom line we're adults....not like flirting with a 20 something year old guy, I guess. So I figure no rush, he'll make his move soon and we'll talk.

A couple of days pass (he was off), I get to work this morning and on my way down to my department I have to pass his door. He's standing in the doorway like the morning welcoming committee and at that time another co worker happened to be walking a few feet in front me. He sees her first and says hi (which is fine)
and while he's saying hi to her I'm lookin right at him prepping a nice smile waiting for his eyes to meet mine (this all took about 3 seconds)...howEVER, as soon as I see he noticed I was behind her he suddenly gets real awkward and instead of looking right at me his eyes shoot up and over me as he blurts out a g'morning (kind of directing the greeting to both me and the lady in front of me-she's like 60 her presence had nothing to do with this)then he swiftly turns around and goes inside.

So I'm thinking, okayyyyyyyy. A couple hours later coming back from outside I started down the hall and he happens to be standing in his doorway again. This time as soon as he sees me coming no eye contact, no hello, just turns around back into his office.

WTH was that? My common sense told me -Not Interested. Okay, smh because why the blatant avoidance? You can still say hi but lose the smile and prolonged eye contact and I would get the hint yet still being polite. Right?

My thing is, I'm used to dealing with 20 something year olds that will pull that inconsistent push/pull crap because they want you to chase them. I'm not sure if an older man like 40 something would maybe..switch up on me for the same game. Being no dummy,my gut told me he realized I was into him and blew me off to show me that he wasn't.

Am I wrong?