Cross bow trophy blackops?

how the hell is it possible to get the trophy on blackops, where you have to pack a punch a crossbow, and then take out 6 zombies by sticking the bolt to a team mate. For one, when your friend is in your cross hairs, you can not shoot. And on the of chance (1 in 1000), that it does let you shoot the cross bow, then as soon as the bolt hits them, it dissapears, and then goes back into your gun, as if your never even shot. AND THEN, if you did get it stuck to them, they will be killed by the zombies before it explodes, and you will not get the trophy. WTF