What happens after you put all 3 tapes in the projector in black ops zombies?

Actually there is only 4 tapes, but you need a team of 4 people each person needs to have a tape it can be online or it could be with some friends each person needs to insert the tape into the projector when each person has inserted it the Zombies will be more senseless them ever before but unfortunetly this will only last for about 5min but is very useful helps get lots a points. Also the tape has a little clip of the Vietnam War, the game is based during the Vietnam war which as you most likely already know.