Questions

I really like this guy from work. We work for different teams, so we don´t interract work-wise. I noticed from my first day at work that he is noticing me and checking me out. Back that time, I was seeing somebody, so I didn´t reciprocate. One day we were both late at work and he introduced himself in elevator. Since that day we started to say hello to each other. I can see that he blushes when he sees me and often is very nervous. Once I didn´t notice him and it looked like ignoring, so he started to ignore me and even acted offended (looking away when I tried to make an eye contact). After I initiated a small talk with him, he greets me and smiles.

This week I started to notice that he stays late at work (I always work in the evening as I prefer to arrive later to work) and even his colleagues started to mock him for that, like "What´s going on with you? You didn´t used to work that late". There are also more signs that he may like me, but he´s never texting or didn´t add me on facebook. Never initiates anything - when I smile, he smiles back, when I say hello, he does too, etc.

Do you think he´s shy or just not interested and I´m just projecting this in my head? Why would he behave this way?