Well, immediate first aid is needed for your sister I should think. Also, everyone should wear jeans and closed toed shoes when visiting the chickens, it helps reduce the impact of unexpected aggression. And take a large stick or rake to keep the bird at a distance. A companion with a large stick can also be helpful. Wear wrap around safety glasses/goggles if you need to put your eyes near the chickens (hen or roo). Chickens love to peck eyes, they just can't seem to help it.
But if you're asking what to do with/about the rooster, you have a couple choices. Many folks consider life too short to put up with a human-aggressive rooster - it can ruin the whole chicken experience, and make a fun hobby a trial. If there are or could be the possibility of children coming into contact with the rooster, I cannot stress how IMPORTANT it is to prevent the roo from EVER being around the kids. Management fails. Often best to get rid of the roo entirely in the way that seems best to you. They can permanently maim and terrify children.
1) Make him into soup. He'll be tasty. The Meat Bird forum has all the info you could ever need on how to safely process chicken at home. Process him before you get any more attached. Practice homesteading skills.
2) Post him for free or minimal cost on Craigslist or farm FB pages, letting people know he's human aggressive and should not go to folks with kids.
3) There are many threads on here of folks who have 'tamed' their roosters, but that has never worked for me. You can try it if you like, as long as you're aware it may not work, and kids are no where near your property ever. Most of the time, once human aggression starts, it doesn't stop regardless of what you try, and you can never fully trust them. It usually gets worse as time goes on. A stressful experience for everyone.
There are many good roosters out there. I'm still looking for mine. Love the hens, but give the roos a year or two before you become attached - most roos show human aggression before that time, and after that window if the rooster is nice, they often stay that way.
Good luck. I'm so sorry this happened to you guys.