Students usually become verbally aggressive when in frustrating situations which they see as being beyond their control; anger and frustration become displaces from those situations onto the nearest target. Explosive outbursts or ongoing belligerent, hostile behavior become this student's way of gaining power and control in an otherwise out-of-control experience. It is important to remember that the student is generally not angry at you personally, but is angry at their world and you are the object of pent-up frustrations.

Acknowledge their anger and frustration, ie: "I hear how angry you are."Get into an argument or shouting match.
Reduce stimulation; invite the person to a quiet place if this is comfortable.Become hostile or punitive yourself.
Allow them to ventilate, get the feelings out and tell you what is upsetting them.Press for explanations for their behavior.
Be directive and firm about the behaviors you will accept, ie: "I cannot listen to you when you yell".Ignore the situation.
Submit a STARs report if you believe that additional outreach would be beneficial.Touch the student.