I NEED HELP! cod 4 invincible glitch!?

i was playing call of duty 4. with a friend. and at the beginning of the game this player from the other team was in are spawn area so all of are team mates tried killing him and he was bullet proof/invincible. can you do me a huge answer and tell me how to do this or give me a link from youtube so i can watch how to do this please :) best answer gets 10 points