For gameobject different ray, logic problem

Hello everybody.

I am creating 2d top camera game. My player can shot by holding mouse button, what I already have done.

Problem is when i move my mouse cursor during shooting. My bullets changes ray what I can understand why, but I don't know how to do it correctly. I mean that bullets which I already fired shouldn't go to new ray.

My only idea is, that I can do:

                 mousePosition = Input.mousePosition;
                 if(Input.mousePosition != mousePosition)
                 {
                     i++;
                 }

and then create an array of ray:

                     ray[i] = Camera.main.ScreenPointToRay(Input.mousePosition);
                     var bullet= Instantiate(Prefab, player.transform);
                     bullet.name = "bullet_"+i.ToString();

But I don't know how to say my bullets that they should go to new ray. Hard to say it, i am not English.

I mean that my bullets are prefabs, and bullet has other script which say where bullet should go.

Please help!