The father of a boy who carried out Michigan’s deadliest school shooting was found guilty of four counts of involuntary manslaughter Thursday. James Crumbley’s conviction came a month after his wife, Jennifer, was found guilty of the same charges. The pair were held responsible for their son Ethan’s shooting rampage that killed four teenagers and left seven others hurt. Ethan was 15 at the time. ALSO READ: Inside the neo-Nazi hate network grooming children for a race war The trial of both parents focused on how they treated their son, and particularly how Ethan was given access to a handgun th…