Silkie hen just attacked and killed two of her chicks

[NewMinouMinou]

She's a first time mum, brooded really diligently and four out of the nine hatched this week.
We've left them in the coop, with mum leaving a couple of times a day for a poo. Put some crumb and some water in the coop; checked them 5-6 times daily, all well.
However, today she took them outside for first time, with dad in attendance and suddenly went bezerk, attacking and killing two.

Seems fine now, back in coop with dad and two remaining chicks, but we're at a complete loss. Both the hen and the rooster are v affectionate and love human company, v tame and responsive.... Any ideas? Kids saw attacks and are devastated.

Thanks

Sorry to read this. Minou. How did she fare with the other chicks? Did you get any advice as to why it happened?

Thanks for responding.
She attacked and killed a third chick and then changed completely, becoming very solicitous to #4, who is thriving.

Both mum and dad are taking excellent care of him/her and it's going really well. We can only assume she felt there was sth wrong with the other three or that our garden isn't safe (there's quite a few cats about, but they've never bothered them).

Just really weird.

That is strange. You're right though, she must've had her reasons. Pleased she is managing her last chick