Why does my ex stare at me? What should I do about it?

Anonymous
Okay so months ago, my ex dumped me over text and I haven't talked to him since and now I pretty much hate him. But I see him all the time at school and he stares at me, and if I look back at him he looks away. It's very noticeable to, his staring. One time I passed him while he was talking to a friend and he stopped talking and stared at me. And the other day I was by his class with one of my friends who has that class with him, but my back was to him while he walked down the hall, and she said he stared at me the whole time. OH and I just got a job at his work, not on purpose though and I start on Monday, it's going to be so weird if I have a shift with him. So should I say something? and why would he even be staring at me so much, he dumped me so I doubt he still has feelings.
Why does my ex stare at me? What should I do about it?
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