Why is my coworker constantly laughing at me for seemingly no reason?

I'll be walking past one of my coworkers and he laughs. I'm not sure why. It has made me uncomfortable being around him in the past, but I'm deciding not to let it put me on edge anymore. Anyway, he acted pretty weird my first day there too. He said he needed to ask me something but never did. Maybe I caused that because sometimes I'm pretty awkward. Or maybe he decided he didn't want to ask it? I'm not sure. Anyway, I tend to naturally smile and one day he was doing some weird clearly overly exaggerated smile at me. Anyway, I don't really fit in at work as it is buuut everyone else is pretty nice to me and friendly. I'm a girl and I work with mostly guys. It's a felon job and most of them are felons (I have a weird habit of googling everyone ha ha). And i come across as more innocent than I am. People are surprised to hear that I can ever get angry or EVER be mean. Which I think is stupid because... I am a human. I get angry. So angry that I worry about it. If pushed I can be mean. I keep things in so when I am mean I can be MEAN... again to the point where I worry about myself. But besides the point. Why does this guy keep laughing at me and acting weird? I am kind of strange so maybe it's about that but not exactly personal. I dont know. Thoughts? I'm one of the few white employees too... so yeah I guess I do stand out.
Why is my coworker constantly laughing at me for seemingly no reason?
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