Many studies seem to be swaying towards children experiencing childhood trauma as being a contributing factor to violence. It certainly is not going to be unusual for men / fathers to be capable of inflicting trauma and abuse.

Not really isolated incident they all may be fatherless but that then means mother failed even then too small a group to draw conclusions of all fatherless boys how many do this very low number

A more important issue is why all the mass shooters in the US are white. Oh, and have access to AK-47s.

Warren Farrell has written much about boys and was interviewed on BOOK-TV at CSPAN this weekend. He did not speak on this point but his talk started me to thinking on it. Among his credentials is that he was once a National Organization for Women board member.