There are 6 year olds that are psychopaths and this is likely one of them.
The worst part is treatment is not a guarantee they can be integrated into society.
It’s tragic for everyone involved but it is true, some people are just missing certain wiring, and being placed in a “loving home” can just mean more bodies and a confused 6 year old not understanding why it’s bad that they killed their parents because they got sent to timeout.