What does it mean if a guy stares at a girl when she's not looking but avoids eye contacts?

Anonymous
Coming from a guy I've had a lot of eye contacts before, who often stared into my eyes intensely, who I heard, said I was hot to his friends and stalked me.
But now I found out he has a girlfriend, I stopped looking at him. But he still, except he doesn't make a lot of eye contacts, especially when we are close to each other.

He now watches me for a long time when he thinks I'm not looking, even follows me with his eyes even turns around when I walk from afar (he can't see my ass from where he is), but once I catch him, he looks away quickly.

What does it mean if a guy stares at a girl when she's not looking but avoids eye contacts?
What does it mean if a guy stares at a girl when she's not looking but avoids eye contacts?
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