The REAL Story:

The dude was pinching Zidanes nipple while a play was going on, after the play the lip reader was able to read what the italian player (Materazi) was saying but not what Zidane was saying because Zidane had his back turned, the Italian player said the following things in order

"Calm down."
"No."
"Liar."
"I wish a horrible death upon your entire familly."
"Go fuck yourself"

That's when Zidane headbutted him in the NECK, not the chest.

And yes, Zidane did learn that his mother was seriously ill a few days before that game, and the italian was most probably refering to that with his comment about his familly dieing.

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