Why would he turn to look at me and look at me until I walked past him?

We used to talk last year and and he broke things off because of ’differences’

after long time he saw me recently. He turn to look at me ( he turned his head) as soon as He saw me from the corner of his eyes. I put my head down because I got nervous. When I looked up he was looking straight in my eyes with serious look. We locked eyes. I then broke the eye contact.

Why did he do that?

Why would he turn to look at me and look at me until I walked past him?
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