I have three kids, 22,18 and 15. The 22 year old and 18 year old used to fight like this, and the 18 year old used to fight with the 15 year old too. Sometimes you have to tolerate the yelling and screaming because children can not regulate their emotions the way adults can and their only way of dealing with them is yelling and crying. As long as they are safe you should take the time out. Go outside and sit in your car if you need quiet and practice some deep breathing. My kids have hurt each other sorta "by accident" in the sense that they would have a meltdown and throw something in anger and it has happened to hurt their sibling. My son got stitches from his sister once, and the sister got a bad bump on her head from the brother. Both girls have broken each other's stuff. We are a very close family and husband and I have modeled appropriate behavior and love for them and they still had meltdowns. I promise you as long as there are still good times where they get along and you are able to model love and compassion, when they get older they will not hate each other.