script gets started two times

I have the following code:

    public GameObject bullet ;

    ...
    GameObject.Instantiate(bullet, transform.position + spawnDistanceBullet * transform.forward, transform.rotation);

bullet has one script assigned, now when I the code above is executed the script is executed two times. I have no clue why though, I added a shot counter - nope for every count I get 2 script executions. I also used GetInstanceID() two different IDs (number difference 20).
I also disassigned the script, I get the following messsage two times:

The referenced script on this Behaviour is missing!
UnityEngine.Object:Instantiate(Object, Vector3, Quaternion)

utterly confused

-edit-
I also tried to create a new prefab and see if the problems goes away, nope still getting the script two times…

Finally, found the problem. I had the script that instantiates the shot running two times (one JS and C# version, the JS version was still assigned to the 3D Model prefab, whereas in the new version the C# script is assigned to a empty GameObject that instantiates the 3D Model prefab, thus it was a bit hard to find…).

MODS: please close