I'm surprised at how this thread has gone. I would have thought there'd be a bunch of btdt stories. I wonder if the lack of them really means that we mama bears are in the minority.
Anyhow, here's my story: When Milo was probably about a year and a half old we were playing with some friends in an indoor play area in a mall. I was standing about a foot and a half away from him, but I was talking to a mom who was sitting several feet away from me, so I wasn't just looking straight at him, but back and forth between him and my friend. I looked down at one point and saw what seemed to be a sweet little girl (I'm sure she was, mostly), 3 or possibly 4 yrs old, sweetly patting him on the head, looked up to my friend, and then when I looked down again, she had four of his fingers in her mouth and she was biting down as hard as she could, like with head shaking from exertion. OMG! I felt like I had been kicked in the stomach. He was my first child and this was the first time anything *bad* had happened to him, and certainly the first time he'd been purposely hurt by another person. I just reacted, did not think about it at all, and had I thought about it, I'm sure I would have behaved differently. But I physically did *something* to that little girl. I moved her with force, though I'm not sure if I pushed her or kind of threw her away from him. And I swear, I think I roared. There was probably only a 3 second period that I really was out of control but I truly don't remember what I actually did and the idea of that has always freaked me out (this was probably 5 1/2 years ago now). The little girl wasn't hurt, thank goodness. But I bet she was kinda stunned by it. And, as a previous posted said, I think maybe it was a good thing to show that girl what my visceral reaction was. My guess is that she had been told many times not to, and probably yelled at and punished and maybe even hit, over biting, but there was something very honest and immediate about my reaction that I'm sure she didn't miss. My reaction wasn't punishing or mean or belittling of her, but it did make clear how her biting made me feel. So who knows, maybe it gave her a reason not to keep biting or maybe it didn't. But I think it was okay in the end.
The good news is... I haven't done anything like that since. It has not been a pattern, at all. There was a post here somewhere where someone seemed to be assuming that you are just a screamer or something, like it's a habit and you reacted that way because yelling is your habit. But I don't think that's what your reaction was about at all. I am not generally a roarer, in fact I believe that was the only occasion in my life where I roared and I never push little kids around. The whole thing felt so much more chemical than that -- like I had a hormonal response, not an "oh, I'm feeling b*tchy bc I'm a woman" kind of hormonal, but a good honest to goodness chemical reaction. I suppose it was probably a good spurt of adrenaline that caused it. And I bet that was the case for you. I really don't think you should beat yourself up about it. I was pretty horrified bc I actually touched the little girl, but the kid you're talking about is not going to be hurt by your yelling. If anything, it could be helpful. Why on earth would a five year old think he'd get away with that sort of behavior in front of the parents of the kid he was being mean to??? Crazy! He may have needed a little dose of reality.