Hatchlings killed

[Japetus]

I've had two hens sat down with five days difference.. The first chicks hatched yesterday -4 out of 8 eggs- but then the hen abandoned the rest of the eggs.
I've tested putting two of those abandoned eggs to the second hen and today I encoured both the little chicks being hatched but killed by the hen -there were pecking marks at their heads..
Was it because she realised that her eggs were not supposed to hatch that early? Did she somehow recognised that the eggs weren't hers?
Should I keep a closer eye on her and remove her own hatchlings as soon as they are hatched in case she does the same to them?
She's a one year old chicken, first time that she sits down for hatching.

 

[slordaz]

@Ridgerunner
@oldhenlikesdogs
tagged someone that might be able to help you better than me, but my thought is if the hen leaves the eggs, either leave them or put in brooder at least if you don't have an incubator handy, Then other hen knows just how many she was sitting on

 

[Ribatutta]

Definitely keep an eye on her. I had a hen sit the whole 21 days on some eggs I gave her. As they hatched she started killing them and eating them.
I took what was left off her and managed to hatch 3 under a heat lamp.
I did a lot of research and the consensus was once they do this it’s likely they will do it again.

 

[Japetus]

Thanks, I will definitely keep an eye on her.