If he really does it, here in Germany his dad would be the only ones who were charged, parents are 100% responsible for their children until they are 14.
I can't tell you for sure, but in Spain anyone under the age of 14 does not have criminal responsability. Now again,I have not heard of any case in spain in wich a child so young has been accused of murder. I haven't heard of any younger than 14.
There was recentely one about a 12 year old girl who confessed to the police to have killed a little boy pushing him through the window, but the police believe she is covering up for her parents that were drug addicts. The parents were arrested. She can not be charged with a crime but she was put under custody for the state, not jail. we haven't heard anything else about it, because being a minor involved there is a gag order on the case.