Well, after the machete JW attacker at the airport, and the elder who killed his own family before that, and all the THOUSANDS of sex abuse cases out there, all combined with the fact that the JWs are a fraction of the size of bigger mainstream denominations/religions....I don't see how there CAN NOT be some correlation between these incidents, and the ultra-high control cult that is the Jehovah's Witnesses.
But yeah...there are plenty of nut jobs of every stripe. And easy access to guns in the US doesn't exactly help.