I told him we should just be friends. Guys please explain his behavior.

I was talking to a guy for like a month and then I told him we should just be friends. He didn't want to but later agreed. Then he sees me with another guy and tells me that he doesn't think we should talk anymore because he's been seeing someone else and she probably wouldn't like it. I asked him if he just didn't want to talk to me anymore, but didn't answer... what does this behavior mean? did I hurt him and that's why he said this
I told him we should just be friends. Guys please explain his behavior.
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