Broody hen pecked 3 chicks

[mi2bugz]

We have a New Hampshire Red first time broody hen that hatched out 1 chick and was still sitting on an egg (2 days later). I am sure it's not going to hatch so we went and got 3 one day old chicks and tucked them under her at night. They were fine when we went out to check on them this am but when I went back to change out water/food the broody hen had pecked 2 to death and 1 was gravely injured. Did I do something wrong? Should she be allowed to have more chicks as long as she hatches them out (left the one she hatched out alone and is taking good care of it)?

She was being such a good mom to her little one that this shocked me!

 

[sourland]

Some times if fostered chicks are a different color than the original chicks or a hen has had time to bond with 'HER' chick/chicks they will not accept fosters.

 

[mi2bugz]

So should I take the unhatched egg out? She keeps pulling it under her but it is now 3 days after her first chick. I don't hear it peeping so I assume it isn't going to hatch. If by chance it does will she take care of it or attack that one also?