AS2 slideshow previous btn issue

import gs.*;
import gs.easing.*;


//---Load XML


var xmlPath = "photos.xml";
var photos_xml = new XML();
photos_xml.ignoreWhite = true;
var imageList:Array = new Array();
photos_xml.onLoad = function(success) {
    if (success) { // ----------- load successful
        // ----------- convert XML content to an array
        imageList = photos_xml.firstChild.childNodes;
        // ----------- Do some action once xml is loaded
        loadImage();
        // ----------- Do some action once xml is loaded
    } else {
        // ----------- problem loading, check path
        trace("Error loading photos_xml");
    }
}

//---Load Images


var currentImage:Number = 0;
var imageLoader:MovieClipLoader = new MovieClipLoader();
var loadListener:Object = new Object();

imageLoader.addListener(loadListener);

loadListener.onLoadInit = function(target_mc:MovieClip, httpStatus:Number):Void {
    TweenLite(dot)to(container_mc.background_mc, 1, {_width:target_mc._width + 20, _height:target_mc._height + 20, ease:Strong.easeOut});
    TweenLite(dot)to(container_mc.border_mc, 1, {_width:target_mc._width, _height:target_mc._height, ease:Strong.easeOut});
    TweenLite(dot)to(container_mc.mask_mc, 1, {_width:target_mc._width, _height:target_mc._height, ease:Strong.easeOut});
    
    // center content
    var clipXTarg = Math.round((Stage.width/2)-((target_mc._width+20)/2));
    var clipYTarg = Math.round((Stage.height/2)-((target_mc._height+20)/2));
    TweenLite(dot)to(container_mc, 1, {_x:clipXTarg, _y:clipYTarg, ease:Strong.easeOut});

    // find previous image
    if(currentImage == 0){
        var prevImgNum = imageList.length -1;
    }else{
        var prevImgNum = currentImage -1;
    }
    var prevImg = container_mc.pics_mc["pic"+prevImgNum];
    TweenLite(dot)to(prevImg, 1, {autoAlpha:0, onComplete:removePrevious});
}

loadListener.onLoadComplete = function(target_mc:MovieClip):Void {
    TweenLite(dot)to(target_mc, 1, {autoAlpha:100, delay:1});
    setTimer();
}


//---Functions List


function setTimer(){
    timer = setInterval(loadImage, 5000);
}

function removePrevious(){
    if(prevImg != undefined){
        removeMovieClip(prevImg);
    }
    
    
    // increment the current image
    if(currentImage < imageList.length -1){
        currentImage = currentImage + 1;
    }else{
        currentImage = 0;
    }
}

    //Load the next image automatically
function loadImage(){
    var loadURL = imageList[currentImage].attributes.imgurl;
    var targetClip = container_mc.pics_mc.createEmptyMovieClip("pic"+currentImage,container_mc.pics_mc.getNextHighestDepth());
    targetClip._alpha = 0;
    clearInterval(timer);


    
    // load the new image
    imageLoader.loadClip(loadURL,targetClip);
}
    //Load the next image if the button was pressed
function loadImagePrevious() {
    if(currentImage == 0){
        var prevImgNum = imageList.length -1;
        
        var loadURL = imageList[prevImg].attributes.imgurl;
        var targetClip = container_mc.pics_mc.createEmptyMovieClip("pic"+prevImg,container_mc.pics_mc.getNextHighestDepth());
        targetClip._alpha = 0;
        clearInterval(timer);
    
        // load the new image
        imageLoader.loadClip(loadURL,targetClip);
        
    }else{
        var prevImgNum = currentImage - 1;
        var loadURL = imageList[prevImg].attributes.imgurl;
        var targetClip = container_mc.pics_mc.createEmptyMovieClip("pic"+prevImg,container_mc.pics_mc.getNextHighestDepth());
        targetClip._alpha = 0;
        clearInterval(timer);
    
        // load the new image
        imageLoader.loadClip(loadURL,targetClip);
    }
}


//---On First Load

photos_xml.load(xmlPath);
stop();



//---Buttons


next_mc.onRelease = function() {
    clearInterval(timer);
    timer = setInterval(loadImage, 500);
    pause_mc._visible = true;
    play_mc._visible = false;
}

prev_mc.onRelease = function() {
    clearInterval(timer);
    ????
    pause_mc._visible = true;
    play_mc._visible = false;
    /*if(currentImage == 0){
        var prevImgNum = imageList.length -1;
    }else{
        var prevImgNum = currentImage - 1;
    }
    var prevImg = container_people_mc.pics_mc["pic"+currentImageNumber];
    TweenLite(dot)to(currentImage, 1, {autoAlpha:0, onComplete:removeCurrent});

*/}