Interesting data point - mass shootings

From Real Clear Politics:

Of 27 Deadliest Mass Shooters, 26 of Them Were Fatherless
After all, it is boys and men who are typically to blame for violent acts of aggression. Ergo, testosterone the defining hormone of masculinity must be to blame. But testosterone has been around forever. School shootings have not.

Makes a lot of sense - a stable family produces stable children.