Why aren't I getting One Bullet One Hit?

In my collision detection code, bullets are deactivated once they have been involved in a collision:

for(int j = 0; j < enemies.size(); j++){
    //check for collision
    if(bullets[i].isActive() && bullets[i].getSprite().collidesWith(enemies.get(j).getSprite())){
    
        //remove bullet  
        removeBullet(i); //bullet is deactivated here, .isActive() will return false
        
        if(enemies.get(j).damage(1)){
            // --snip--
        }
        break;
    }
}

The only place bullets are deactivated is in this section of code. The only place they are activated is when they are created.

Despite this a bullet will inflict damage multiple times. removeBullet() triggers an explosion animation, and this plays multiple times. What could be going wrong?

Update

Here's removeBullet()

private void removeBullet(int i){
    if(bullets[i] == null) return;
    bullets[i].deactivate();
    makeSmallExplosion(bullets[i].getSprite().getX(),bullets[i].getSprite().getY());
    bulletPool.recyclePoolItem(bullets[i]);
   开发者_StackOverflow社区 bullets[i] = null;
}

More than one thread may be running? Alternatively it might not be a problem with removing the bullet. But there are multiple bullets at that position and/or enemies?

Ah AndEngine; I'm actually a Mod on the forum :)

I've wrote this blog post about object pools in case you need to check the way you've implemented yours: http://c0deattack.wordpress.com/category/programming/andengine/

I wonder if you're recycling the bullet properly?