Danita: I'll be praying for your brother and his heartache. It's terrible to lose a pet.

As for the adults being responsible for keeping an eye at her and keeping her safe, you're absolutely right!

The girl needs to understand that what she did is wrong. Her action must have a consequence that will help her learn, but that will not harm her in any way. I believe it is best if he and her mother talk about it and decide together what the best course of action should be.

And... be aware! Kids need 24/7 supervision.
Have a good day!