Sorry to hear that. That why you always have to watch for signs of aggression when mating birds. If one to aggressive, it best to separate them. It a tricky process that breeders have to do. I seen to many incidents over the years even with experienced breeders and proven pairs. They can be best friends for years and when they decide to mate and female lays eggs is usually when things can go very wrong, or male get to dominating and controlling. This is when you watch careful for sign of aggression from one, or another and separate if needed. Now I had pairs that got along full life, so really depends on the temperament of the birds. Some just do not make good parents and way to aggressive and they should not be allow bred and be separate and the aggressive one not allow to mate and kept separated. As bad as it sounds, sometime breaking the bond with the two birds is best, then having a dead, or injured bird. Then you can mate the other non aggressive bird to another female, or male later on. The aggressive one just bond to you and keep separated, or if a breeder re-home and sell, or give to a family that has no other birds that will give attention to him/her. As they do get depressed and cause plucking, or destructive behavior otherwise.
I learned this when I was young and worked for a experienced breeder for years, so seen it all.
For some reason notice with Indian ringneck, or Eclectus females are usually the aggressive ones that attack the male, or over protective of their young, usually the other way around for most other species of parrots.