We have one of those too. He attacks both of my kids, the dog and the cats so tomorrow he is on the cull list. Too scarey what could happen. He draws blood out of the blue, just chases them down when they are walking away or just playing on the lawn. Crazy idiot. I know it will be hard but cull him.
send ya child in there with a broom, and tell her to play hockey with him,, bat him round for 20 minutes,, then see if he does it,, if not,, he just needed a lesson, just like our kids do,,if he keeps it up,, cull him ,, but you should be able to teach them both to get along,, very few roo's are totally mean,, would be awful to cull if he was just having a bad day,,, their like us,, not all days can we be great people.
EDIT: ta say ,, sometimes roo's are just being roo's ,, some days 1 of mine are having a bad day, i can tell the minute i see him,, and the kids and wife are told to leave him alone,, if they dont, and he flogs them,,, THEY get the "speech" cause it was their fault.
How old is the rooster, how old is the child, what was happening when the roo attacked, etc. Too many variables to just say "cull it". Is the roo going through his adolescence? Is the child a very small child and thus seems a "threat" or "rival" or "intruder" in the eyes of the roo? Was something else happening that had the flock upset? IMHO some people on here are WAY too quick to say "cull" i.e. "kill" when some rehabilitation will work wonders on lots of roos ESPECIALLY if they've "always been friendly" as you say yours has. GIVE HIM A CHANCE! Read RoosterRed's page on roo behavior/rehab, separate him from your child or vice versa, and give the roo a chance to grow up if he's not already mature. If he is, a little behavior modification may make all the difference in the world.