Wow! 3 pages of replies!! Thank you all!
First of all, I don't know what breeds our chickens are. I just say they are chickens. %)
Second, when he attacks, no one is laying and it is not like my kids are being noisy (or even talk at that moment - very often, like this morning, my son would come to me feeding them right after he awakes - he would get up, cry for mama, dh would dress him and send to me - so when ds comes, he does not talk at all. He is very quite, like if now fully awake). It feels like the roo just wants to say: hey, I am the boss here! Just to show my son that he, the roo, is higher in hierarchy.
Today I was right there, by my son, and we always try to watch the roo, since we know now that he might attack - just my reaction was not quick enough to get the roo before he got onto my son - it all happens in less then a second, probably. I was shocked that the roo attacked this time with me being right near my son.
I guess, we'll cull this roo and will be watching others (growing) for which one to pick.
This one used to be beautiful (until molting - see pics in my second link) - he was never able to grow feathers back in front of his neck - his chickens peck those feathers right out, just when they start to grow. Besides letting his hens do that, he also never eats the treats - always leaves those to his hens, same with any yummies he finds - he does not eat - he calls for his hens to come and eat what he found.