Domestic issue....apparently bad relationship with wife. Daily Mail rported that th owner regularly invited some and not others for special events...he was not invited. Whatever that means I see this as a disgruntled husband full of anger and revenge takes it out on those in that dance studio.
Would be interesting to know if his wife was one of those shot...and if or not she lived.
Used to be most people grew out of that kind of insanity when they got to be 72.