ActionScript 2.0 :: Game Project - Placing Unique Instances Of Enemies On Screen

I've been working on a uni project. Basically, enemies are placed on the screen using a timer variable and using the attachMovie to put them on the screen. This is an example of the code I'm using:

Actionscript Code:
var enemies;var timer;
function onLoad(){
enemies = [];
timer = 0;}
function onEnterFrame(){timer++;
if (timer == 10) {
Timer = 0;
var enemy = _root.attachMovie("mc_1", "mc_1",
_root.getNextHighestDepth());
enemies.push(enemy);
}}

This works and places them on the screen, (and into the array) but by putting them into the array, I thought that each one would be a unique instance of the movieclip which doesn't always seem to be the case. If I shoot one of the enemies, sometimes another enemy will explode (or both of them) and other times I will knock into one enemy and another one will be the one who get's knocked.

For my collision code I'm using this:
Actionscript Code:
for(var i in _root.player.enemies){
if (some arguments..)
_root.player.enemies[i].health -= 10;
}}
The explosion code also uses a similar for loop. Should I look at another method to place unique instances of the enemies on the screen?