There is this older man that I work with. He is like 25 years older than me. I realized that he behaves kind of different with me than with others. Once he was talking and laughing with some of our colleagues and I was behind him , but a little far away from them and next to them were some of my friends and I told them hi and in the moment he heard my voice he stopped talking and laughing and he turned around and started to stare at me without smiling. He was watching my move. His body and his head was moving after me. Then a told him “hi “ and he stared for a few seconds and then he continued to do this until I broke his stare. The weird thing was that other colleagues told him “hi “ and were there and he didn’t stop talking or laughing. It was weird. Another time I was talking with him alone and when he finished talking he stared into my eyes without smiling until it made me feel uncomfortable so I broke his stare. And I told him “thank you for helping me “ and I left , but when I got to the door he started to talk again and he said something funny and I laughed. I just don’t understand. Why does he behave this way?