I, I've got some code that calls a routine to throw an object when the P key is pressed, it all works fine except every time I press the P key he throws the object + 1 more every time, I'm using (Input.GetKeyDown) can someone please point out the obvious that I'm missing please.

var ThrownObject : Transform; // Set var for a object to throw
var Explosion : Transform; // Set var for the exposion to use

function Chuk()
{
  animation["Throw"].layer = 1;
    animation.CrossFade("Throw",0.2);
       animation["Throw"].blendMode = AnimationBlendMode.Additive;

var throwObjectEvent = new AnimationEvent();
  throwObjectEvent.functionName = "throwObject";
    throwObjectEvent.time = 0.5;

animation["Throw"].clip.AddEvent(throwObjectEvent);
}
function throwObject()
{
// Add a (var ThrownObject : Transform;) at top of script then drag the object you want
// to throw into it in the inspector window
var bullit = Instantiate(ThrownObject, GameObject.Find("throwSpawnPoint").transform.position, Quaternion.identity);
    bullit.rigidbody.AddForce(transform.forward * 2000);
       var bang = Instantiate(Explosion, GameObject.Find("throwSpawnPoint").transform.position, Quaternion.identity);
}