StateMachineBehaviour is working weird with AnimationClip.AddEvent

So, StateMachineBehaviour.

 using UnityEngine;
 using System.Collections;

 public class AnimatorStateBehaviour : StateMachineBehaviour {
 void OnStateEnter() {
     DoSomething();
 }

it will fire once when animator is entering any status. right? it should fire once. but it's working weird when I'm trying to use 'AnimationClip.AddEvent'. in it.

 using UnityEngine;
 using System.Collections;
 
 public class AnimatorStateBehaviour : StateMachineBehaviour {
     
     void OnStateEnter()
    {
         AnimationEvent evt = new AnimationEvent ();
           evt.functionName = name;
           evt.time = time;
     
          ... get clip from AnimatorClipInfo ...

           someClip.AddEvent (evt);
     }

now I've added 'AnimationClip.AddEvent'. and let's play it.

well... it goes crazy.

this thing fire function every frame! what's wrong with this? I can't use AddEvent in StatusBehaviour?

Do you have any idea what is wrong with function? any comment will be very helpful.

Thank you!