Oh, what an abysmal, mean-spirited little man. Having to tear down those around himself as part of his daily existence is a pathetic way to live.
I'm so glad your boss told him to leave and not return. Like your dad, he did the right thing. These are decent human beings, with an intact sense of empathy toward others, including you. They acted to try and prevent further attacks on you by this little monster.
Please don't take yourself to task for how you behaved under extreme emotional duress. You're a decent human being, with emotions and empathy, and being so viciously and irrationally attacked by someone while simply existing and doing your job is a terrible experience, and one nobody should be planning or rehearsing for.
Coming here and sharing the experience, and finding support is a good move on your part. I think we all empathize with you, and many of us have shared in this sort of experience. We survived it, as you did. Don't let it alter your thinking about yourself. The opinions of someone so obviously unsane, who has excised themselves from the human race, cannot matter to us.
I think we're all proud of you, and wish nothing but the best for you. I'm sorry you had to have this brush with evil.
Hugs, Michelle