Your reaction is normal. He was not a safe person. Just because he's acting safe now, doesn't mean he's safe. You need to stay safe, and one of those ways is not to let him find out.
They can change at any moment. For example...
A section from the last email I got from my ex-boyfriend:
I don't hate you. I'm not sure what you think of me, but I only want you to be happy. I handled things all wrong and I'm an ass for that. [Snip! Bunch of rambling about some drama in his life.] I know you don't care, sorry. I can never thank you enough for helping me save this place. Thank you. I'm sorry I'm rambling. Good luck with your New Home! I'm very happy for you. If you need to borrow any tools, ever, just ask, I deliver too. ;-) Good night.
An email a ways before that:
I'm probably having neck surgery within the next few weeks. And I'm being told I'll be out of work for 2-4 months. I am not sure how I'll be able to make payments [on the money I owe you] when that happens. I'd really appreciate any ideas you may have, so I'm not hurting you financially during that time. You don't have to respond to this email and I'm sorry I'm bothering you. But this has to happen as I can no longer move my head at all. Again sorry, but I figured you should know this ASAP.
All nice and polite and generally inconspicuous for a normal person, right?
The problem is that this one came in the middle, after I responded to the one above with a suggestion on how as long as he paid me his regular payment through September so I could use it for buying my house, that I'd be okay if he skipped the next few months after as long as he kept me up to date on his doctor's notes about him working:
I need to start by saying my surgeon and I agree that my surgery will be put off as long as possible. I will not be having surgery anytime soon. Neck injections and painkillers for now...
I completely understand about getting on with your life... I don't want anything to do with you. I don't want you around my daughter at all... I am considering getting a restraining order to keep you away from me. And the district attorney has told me I could press charges on you for terroristic threats. I've done nothing but try to be your friend... The only emails you will be getting from me will be regarding money. I hope you understand.
So... I hit a nerve, and he lashed back to try and hurt me instead. And that's how he does it. It has nothing to do with me, but he's nice and polite when he wants something from me (LIKE MY NEW ADDRESS!) and cruel and hurtful when I attempt to hold him to any semblance of responsibility. He doesn't have surgery scheduled! And so how could he provide the doctor's information I requested to get out of paying me? And so he lashed back, like a cornered snake, because that's all he is.
Past behavior is the best indicator of future behavior. Just because he's nice now doesn't mean he'll be nice later. Do not beat yourself up about your reaction - you are staying SAFE!
I strongly recommend a book, The Gift of Fear. CAUTION: There are some rough subjects in here, so I would not read this book if you are easily triggered by such (true!) stories yet. But when you can, read the book. It's about trusting our instincts rather than trying to talk ourselves out of it "to be nice."
As another note, if you take your set of keys in your pocket and slip a key between each finger, it makes a rather convenient weapon that you'll always have available (as long as you don't lock yourself out!) - and you can slip your thumb through the keyring to make sure you keep a good grip on them.