Lock up or discard all guns. Eliminate all violence within the family. Parents need to model a non-violent response to anger. Humiliation is a psychological slap in the face. Empower parents to react quickly to a threat of violence.
All threats are to be considered serious.
Don't hesitate to call the police. Discontinue the playing of violent video games and strictly monitor TV, movies and on-line activities. Give strict consequences for alcohol and drug use. Then the therapy begins. Kids need to learn to connect to the world in a way that is human and real.