I think that what your boyfriend did to you has understandably left you feeling degraded and betrayed. 4 years of commitment deserves a discussion to end it, and some sense of emotional closure that you were not given by his not allowing you to communicate face-to-face with him in a respectful manner. Anger is a stage in processing grief and loss. In many ways I feel he deserved your anger at that moment, and likely a lot sooner, and you should not feel guilty for feeling the way you do. Your anger is part of processing betrayal and loss, and even though it isn't deemed healthy in our culture to express anger, it actually is. I would say he likely needed to hear all of what you likely said to him.

You seem like a good person, and I can tell you would never do to someone what he has done to you. Allow your emotions to come as they will, most important I think is to fully recognize and understand why you are angry, which you seem to have a good connection with. As far as I can tell here I see nothing to feel guilty for, as you did nothing wrong.