Please read this: "call police"

http://www.minti.com/parenting-advice/11696/When-Kids-Get-Ugly-How-to-Stop-Threats-and-Verbal-Abuse/
Intimidation and Threats of Violence (by the child)
If a parent is frightened about physically destructive behavior, destruction of property, or threats of violence, I want to be very clear about this: Call the police. It’s very simple.