However you look at this it is a tragic event. One thing which the JW teachings offer people is an identity. To be connected with others is a human urge. If you have very little going for you in life then simple things like belonging to a religion can mean a lot. If you are then expelled from that community your lifeline has gone and if your reasoning and emotional control is poor then this situation could arise although fortunately this must be rare.
I did read of a JW missionary in the Pacific islands who killed his two missionary companions.