How to hide enemy when hit in slick2d

Question

I'm creating a 2d game in slick and im having a bit of trouble when a bullet hits an enemy The bullet hits the enemy and it registers as being dead- but I don't know how to remove the enemy image from the screen. Below is the code:

This is in the render method:

      for(Zombie z: zombies){       

        if(!z.isDead()){
            z.render(gc, sbg, g);
        }

    }

all i have in the Zombie render method is

     g.drawImage(zombie, 100, 100);

I'm sure it will be something simple, but after a while of searching I'm struggling to find anything relevant - any help will be greatly appreciated!