ActionScript 3.0 :: Buttons And Random MovieClip - Calling Array

I'm learning AS3. I would like to call an Array which contains five mc. Although when I check for errors on the script it says that it doesn't have errors, when I test the movie I have a
couple of errors.
1046 Type was not found or wan not a compile...
1180 Call to a possibly undefined method
placeRandomPicture();

Here is my script.
var listLoader:Array = new Array(back_1, back_2, back_3,back_4, back_5);
bt_1.addEventListener(MouseEvent.CLICK,
function (evt:MouseEvent): void {
function placeRamdomPicture (): void {
var iRandomImage = Math.round (Math.random() *
listLoader.length-1);
iRandomImage = (iRandomImage > -1) ? iRandomImage : 0;
picHolder.addChild(new listLoader [iRandomImage]);
} placeRandomPicture();
});