Guy's Behavior

Why is he all the sudden initiating conversation (Details in description)?

So, I have a guy friend (17), who I (16) always initiate conversation with. If he's in the hall, I'm the one to say hi, same situation with texting. But recently, he has been initiating conversation. I will just be walking in the hall, and I'll hear him go, " Hey ___! " And keep walking. It's throwing me slightly off guard. And recently, he has been messaging me good night and good morning, when I'm always the one that does that.
Guys, and girls, what is going on? Has he all the sudden became interested in me, or is he just getting to know me more?
Why is he all the sudden initiating conversation (Details in description)?
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