Guy's Behavior

Why would a married man show signs of interest in another female? (Or maybe I'm reading to far into this situation)?

Why would a married man show signs of interest in another female? (Or maybe I'm reading to far into this situation)? This guy used to always stare and smirk at me whenever he saw me, and he would also always greet me. I saw him in the neighborhood, and we held eye contact for a long time. My sister even noticed him staring at me. I was walking to my car, and I noticed him staring at me from a distance.(He was sitting on a bench). I haven't seen him in a while, but he saw my sister and asked her about me. (How was I, what grade/school). When I saw him again, (I volunteer at a school that his son goes to) he looked at me then looked away. (Casually). Then before he left, he gave me this sad stare. (Well, not really sad, but he didn't give me that "look" like he usually does). I do admit that he's very attractive. I haven't done anything except try to be nice to him and his wife. But I can tell that she hates me by the way she looks at me and how she ignores me when I speak to her.
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+1 y
I'm a senior in high school and the guy and his wife are probably in their 30's-40's. I don't want to be stuck in a sticky situation.
Updates
+1 y
This is my second time asking this question, so how come when I asked this question the first time (I left out that he was married) and the answers that I got were, he's interested/attracted. But when I added the information that he was married, I get stay away/he's not interested?
Why would a married man show signs of interest in another female? (Or maybe I'm reading to far into this situation)?
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