How do you know if you hurt a guys feelings?

So me and my boyfriend has been having problems and honestly I'm sick and tired of him & how he treats me and he's always giving me mixed feelings so I don't know how he feels about me.. anyways I decided to break things off with him but also letting him know we can be friends just no more of us and i guess he took it the wrong way and got all mad started cursing me out, threatening me and saying really really mean hurtful things to me & I honestly didn't want to hurt him when I decided to break up I just didn't wanna be with him no more. The thing with him is that he never expresses his feelings towards me and always acts so cold and distant like he doesn't care about me and I tend to over think a lot and have to constantly guess what he's thinking and how he feels about me so I never knew if he had feelings for me or not.. but when I broke up with him that's when he truly expressed himself and it was very hurtful. Did I end up hurting his feelings causing him to react like that or what?
How do you know if you hurt a guys feelings?
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