Will my hens keep attacking other hens?

I apologize if this a redundant post, but...I started with 7 hens and when they were about 6 months old (mixed NHR and BA), integrated 9 (mixed variety) 3 and 1/2 month old hens with them with no major problems. Typical sorting of the pecking order. My neighbor then gave me 5 Red Sex Link hens and same thing, a little squabbling but no feather loss or blood. I had 3 other hens that are about 3 1/2 months old now. I attempted to integrate them in the same way I did the others, put them in the coop with the big girls at night and in the morning, everything seemed fine. They were bullied a little more but no feather loss that I could see. On the 2nd day (yesterday), the smallest of the 3 new girls was missing. The other two had huddled themselves together into one nesting box. I have a camper-converted-coop and thought maybe the other hen was roosting on one of the axles, which sometimes happens. Today I found her dead under the coop with all the feathers off her head and a hole pecked in her head. Inside the coop, there were blood smears on the waterer and feeder where the culprit(s) had fed. I found dried blood on one of the sex links. I stayed in the coop a while and noticed a few other of the sex links seemed to be pecking and bullying the remaining 2 smaller hens more so. I did remove those two back to the brooding area. So, what should I do? Wait until they get bigger to mix? Get rid of the one hen I know for sure killed the other? I have read comments that Red Sex Links can be bully birds. Anyone's thoughts, opinions or advice would be greatly appreciated!

 

Sorry I haven't posted back. I have 20 birds since the one died and the camper is approximatly 8x10-maybe 8x12. They've all established their pecking order now with no further "major" issues. I really believe it's the red sex links, they just seem to be more aggressive than the other birds.