I would have rung the dinner bell on him immediately. Same-day cull! Roosters kill and main toddlers, children, and older people rather too frequently. If he attacked a chick beyond a gentle disciplinarian peck, I'd cull. If he attacked me in any way whatsoever, I'd cull. In the wild Jungle Fowl, the ancestors of chooks, are devoted family members.
It is unnatural for them to attack a chick or human like that. Domestic Jungle Fowl/chooks are intelligent enough to know what is a threat and what's not. The hand that feeds is not a threat. I cull hens and roosters alike for baby-bullying. They tend to show their preference or predilection for beating up on babies at a young age, before six weeks. I've only had one rooster attack me out of the hundreds I've raised, and I didn't breed that one myself. He went for the face without warning or provoking, twice; just flew at me from the ground, I automatically slapped him away defending my eyes, and he was straight back the next instant.
It's normal for them to gently peck an errant baby, but if they are actually hurting it, that's a severe warning sign. A breeding rooster's not worth anything if he's damaging or destroying chicks. I always ran many roosters with the flock and never had any jealousy issues. It could be that he wasn't raised with a normal family flock situation so he doesn't recognize chicks, though? How he and his recent ancestors were bred and kept has a lot to do with it. Though I do think that if he's attacked people, you should cull as a rule, because otherwise you are potentially breeding the sort of chook that kills babies. I don't know how common that is where you live but in Australia a lot of folks keep savage roosters and toddler killings aren't really uncommon. They just think he's protecting the flock. From what? Grain?
