I got no proof other than my personal experiences growing up and observing kids while teaching them in groups at a school.
Children by in large seem to have little empathy for others. Children have little to no problem with bullying others without any emotional issues. Even to the point of pushing other kids to suicide. They have little regard for others and even less control over maturity.
I think empathy is something that you develop as you grow older. It’s more a mark of adulthood than childhood.
He didn’t actually kill the intruder so that’s something he can probably look forward to either after joining the military or law enforcement.
But joking aside, children by in large, don’t seem to have much empathy about such things. You can see this in the bullying they do in schools and on the playgrounds. And it doesn’t seem to bother them much.